Here is some error output and the relevant screenshot of the GUI when hanging.
alu.tst on winxp, java folders jre1.6.0_07
Exception in thread "Thread-31" java.lang.ClassCastException: sun.java2d.NullSur
faceData cannot be cast to sun.java2d.d3d.D3DSurfaceData
at sun.java2d.d3d.D3DRenderer.copyArea(Unknown Source)
at sun.java2d.d3d.D3DSurfaceData.copyArea(Unknown Source)
at sun.java2d.SunGraphics2D.doCopyArea(Unknown Source)
at sun.java2d.SunGraphics2D.copyArea(Unknown Source)
at javax.swing.BufferStrategyPaintManager.copyArea(Unknown Source)
at javax.swing.RepaintManager.copyArea(Unknown Source)
at javax.swing.JViewport.blitDoubleBuffered(Unknown Source)
at javax.swing.JViewport.windowBlitPaint(Unknown Source)
at javax.swing.JViewport.setViewPosition(Unknown Source)
at javax.swing.JViewport.scrollRectToVisible(Unknown Source)
at javax.swing.JComponent.scrollRectToVisible(Unknown Source)
at HackGUI.Utilities.tableCenterScroll(Unknown Source)
at HackGUI.FileDisplayComponent.setSelectedRow(Unknown Source)
at HackGUI.ControllerComponent.setCurrentScriptLine(Unknown Source)
at Hack.Controller.HackController.miniStep(Unknown Source)
at Hack.Controller.HackController.singleStep(Unknown Source)
at Hack.Controller.HackController.access$000(Unknown Source)
at Hack.Controller.HackController$SingleStepTask.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)