JavaFX 1.2 applications that are run in the sandbox are not able to take advantage of Direct3D acceleration, and will default to CPU/SIMD instead.

Here is a simple example that can be used to reproduce this issue:
var graphicsConfig = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
println(DropShadow {}.getAccelType(graphicsConfig));

When run from with full permissions it will return the expected value of : Direct3D
When run from within an unsigned webstart application it will return: CPU/SIMD

You can simulate the same exception by trying to access the RSLRender class directly:
Class.forName("com.sun.scenario.effect.impl.j2d.rsl.RSLRenderer");

Which will result in the following exception:
java.security.AccessControlException: access denied (java.lang.RuntimePermission accessClassInPackage.sun.java2d.pipe.hw)
at java.security.AccessControlContext.checkPermission(Unknown Source)
at java.security.AccessController.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPackageAccess(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at org.jfxtras.scene.effect.RenderTest.javafx$run$(RenderTest.fx:12)

Credit to Steven Herod for uncovering this issue with his Leadfoot acceleration testing program:
http://blogs.herod.net/javafx/2009/07/javafx-effects-and-hardware-acceleration/