We have a test called GradientPaintTest, launch the test by IE7, when you select radialGradient and change the offset value, it threw exceptions.
The test case is attached and exceptions as following:

basic: Starting applet
basic: Applet started
basic: Told clients applet is started
Exception in trigger:
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.scene.paint.Gradients$Factory6.createRadialGradientPaint(Gradients.java:118)
at javafx.scene.paint.Gradients.createRadialGradientPaint(Gradients.java:49)
at javafx.scene.paint.RadialGradient.createPaint$impl(RadialGradient.fx:87)
at javafx.scene.paint.RadialGradient.createPaint(RadialGradient.fx:68)
at javafx.scene.paint.RadialGradient.getAWTPaint$impl(RadialGradient.fx:76)
at javafx.scene.paint.RadialGradient.getAWTPaint(RadialGradient.fx:68)
at javafx.scene.shape.Shape$7.onChange(Shape.fx:190)
at javafx.scene.shape.Shape$7.onChange(Shape.fx:188)
at com.sun.javafx.runtime.location.ObjectVariable$2.action(ObjectVariable.java:165)
at com.sun.javafx.runtime.location.ObjectVariable$2.action(ObjectVariable.java:162)
at com.sun.javafx.runtime.util.AbstractLinkable.iterate(AbstractLinkable.java:55)
at com.sun.javafx.runtime.location.ObjectVariable.notifyListeners(ObjectVariable.java:162)
at com.sun.javafx.runtime.location.ObjectVariable.replaceValue(ObjectVariable.java:117)
at com.sun.javafx.runtime.location.ObjectVariable.update(ObjectVariable.java:145)
at com.sun.javafx.runtime.location.AbstractVariable.invalidate(AbstractVariable.java:179)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:141)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:135)
at com.sun.javafx.runtime.util.AbstractLinkable.iterate(AbstractLinkable.java:60)
at com.sun.javafx.runtime.location.AbstractLocation.invalidateDependencies(AbstractLocation.java:162)
at com.sun.javafx.runtime.location.AbstractLocation.invalidate(AbstractLocation.java:115)
at com.sun.javafx.runtime.location.AbstractVariable.invalidate(AbstractVariable.java:177)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:141)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:135)
at com.sun.javafx.runtime.util.AbstractLinkable.iterate(AbstractLinkable.java:60)
at com.sun.javafx.runtime.location.AbstractLocation.invalidateDependencies(AbstractLocation.java:162)
at com.sun.javafx.runtime.location.AbstractLocation.invalidate(AbstractLocation.java:115)
at com.sun.javafx.runtime.location.AbstractVariable.invalidate(AbstractVariable.java:177)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:141)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:135)
at com.sun.javafx.runtime.util.AbstractLinkable.iterate(AbstractLinkable.java:72)
at com.sun.javafx.runtime.location.AbstractLocation.invalidateDependencies(AbstractLocation.java:162)
at com.sun.javafx.runtime.location.IntVariable.notifyListeners(IntVariable.java:172)
at com.sun.javafx.runtime.location.IntVariable.replaceValue(IntVariable.java:98)
at com.sun.javafx.runtime.location.IntVariable.setAsInt(IntVariable.java:117)
at javafx.ext.swing.SwingSlider$1ChangeListener$anon17.stateChanged(SwingSlider.fx:108)
at javax.swing.JSlider.fireStateChanged(Unknown Source)
at javax.swing.JSlider$ModelListener.stateChanged(Unknown Source)
at javax.swing.DefaultBoundedRangeModel.fireStateChanged(Unknown Source)
at javax.swing.DefaultBoundedRangeModel.setRangeProperties(Unknown Source)
at javax.swing.DefaultBoundedRangeModel.setValue(Unknown Source)
at javax.swing.JSlider.setValue(Unknown Source)
at javax.swing.plaf.synth.SynthSliderUI$SynthTrackListener.mouseDragged(Unknown Source)
at java.awt.Component.processMouseMotionEvent(Unknown Source)
at javax.swing.JComponent.processMouseMotionEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedConstructorAccessor10.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at javafx.scene.paint.Gradients$Factory6.createRadialGradientPaint(Gradients.java:115)
... 61 more
Caused by: java.lang.IllegalArgumentException: Keyframe fractions must be increasing: 0.15
at java.awt.MultipleGradientPaint.<init>(Unknown Source)
at java.awt.RadialGradientPaint.<init>(Unknown Source)
at java.awt.RadialGradientPaint.<init>(Unknown Source)
... 65 more
Exception in trigger:
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.scene.paint.Gradients$Factory6.createRadialGradientPaint(Gradients.java:118)
at javafx.scene.paint.Gradients.createRadialGradientPaint(Gradients.java:49)
at javafx.scene.paint.RadialGradient.createPaint$impl(RadialGradient.fx:87)
at javafx.scene.paint.RadialGradient.createPaint(RadialGradient.fx:68)
at javafx.scene.paint.RadialGradient.getAWTPaint$impl(RadialGradient.fx:76)
at javafx.scene.paint.RadialGradient.getAWTPaint(RadialGradient.fx:68)
at javafx.scene.shape.Shape$7.onChange(Shape.fx:190)
at javafx.scene.shape.Shape$7.onChange(Shape.fx:188)
at com.sun.javafx.runtime.location.ObjectVariable$2.action(ObjectVariable.java:165)
at com.sun.javafx.runtime.location.ObjectVariable$2.action(ObjectVariable.java:162)
at com.sun.javafx.runtime.util.AbstractLinkable.iterate(AbstractLinkable.java:55)
at com.sun.javafx.runtime.location.ObjectVariable.notifyListeners(ObjectVariable.java:162)
at com.sun.javafx.runtime.location.ObjectVariable.replaceValue(ObjectVariable.java:117)
at com.sun.javafx.runtime.location.ObjectVariable.update(ObjectVariable.java:145)
at com.sun.javafx.runtime.location.AbstractVariable.invalidate(AbstractVariable.java:179)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:141)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:135)
at com.sun.javafx.runtime.util.AbstractLinkable.iterate(AbstractLinkable.java:60)
at com.sun.javafx.runtime.location.AbstractLocation.invalidateDependencies(AbstractLocation.java:162)
at com.sun.javafx.runtime.location.AbstractLocation.invalidate(AbstractLocation.java:115)
at com.sun.javafx.runtime.location.AbstractVariable.invalidate(AbstractVariable.java:177)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:141)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:135)
at com.sun.javafx.runtime.util.AbstractLinkable.iterate(AbstractLinkable.java:60)
at com.sun.javafx.runtime.location.AbstractLocation.invalidateDependencies(AbstractLocation.java:162)
at com.sun.javafx.runtime.location.AbstractLocation.invalidate(AbstractLocation.java:115)
at com.sun.javafx.runtime.location.AbstractVariable.invalidate(AbstractVariable.java:177)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:141)
at com.sun.javafx.runtime.location.AbstractLocation$4.action(AbstractLocation.java:135)
at com.sun.javafx.runtime.util.AbstractLinkable.iterate(AbstractLinkable.java:72)
at com.sun.javafx.runtime.location.AbstractLocation.invalidateDependencies(AbstractLocation.java:162)
at com.sun.javafx.runtime.location.IntVariable.notifyListeners(IntVariable.java:172)
at com.sun.javafx.runtime.location.IntVariable.replaceValue(IntVariable.java:98)
at com.sun.javafx.runtime.location.IntVariable.setAsInt(IntVariable.java:117)
at javafx.ext.swing.SwingSlider$1ChangeListener$anon17.stateChanged(SwingSlider.fx:108)
at javax.swing.JSlider.fireStateChanged(Unknown Source)
at javax.swing.JSlider$ModelListener.stateChanged(Unknown Source)
at javax.swing.DefaultBoundedRangeModel.fireStateChanged(Unknown Source)
at javax.swing.DefaultBoundedRangeModel.setRangeProperties(Unknown Source)
at javax.swing.DefaultBoundedRangeModel.setValue(Unknown Source)
at javax.swing.JSlider.setValue(Unknown Source)
at javax.swing.plaf.synth.SynthSliderUI$SynthTrackListener.mouseDragged(Unknown Source)
at java.awt.Component.processMouseMotionEvent(Unknown Source)
at javax.swing.JComponent.processMouseMotionEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedConstructorAccessor10.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at javafx.scene.paint.Gradients$Factory6.createRadialGradientPaint(Gradients.java:115)
... 61 more
Caused by: java.lang.IllegalArgumentException: Keyframe fractions must be increasing: 0.1
at java.awt.MultipleGradientPaint.<init>(Unknown Source)
at java.awt.RadialGradientPaint.<init>(Unknown Source)
at java.awt.RadialGradientPaint.<init>(Unknown Source)
... 65 more