Animation uncatched exception under Windows

Bug provoking freeze in all stages / scenes, blocking every display.
Appears under Windows 7 at least, with javafx 2.1 and 2.2 latest upgrades.
With complex scenes and animations, no test case to reproduce it as I have no idea where it comes from.
Stack trace :

java.lang.NullPointerException
at com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(AbstractMasterTimer.java:366)
at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(AbstractMasterTimer.java:289)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:456)
at com.sun.javafx.tk.quantum.QuantumToolkit$9.run(QuantumToolkit.java:329)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
at com.sun.glass.ui.win.WinApplication$2$1.run(WinApplication.java:67)
at java.lang.Thread.run(Thread.java:722)

Reached after several minutes using the app. Really problematic.