This is a threading issue: during startup, the color and image registries are initialized in the CommonUIPlugin, but two (or more) threads are using the color registry when the editor is started; one of these threads initiates the registry creation and is interrupted by the other thread which attempts to use it before it has been properly initialized.

The result is that an SWT exception is thrown. Stack trace follows:

org.eclipse.swt.SWTException: Failed to execute runnable (java.lang.IllegalArgumentException: Argument cannot be null)
at org.eclipse.swt.SWT.error(SWT.java:4083)
at org.eclipse.swt.SWT.error(SWT.java:3998)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:137)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3527)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3174)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2629)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2593)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2427)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:670)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:663)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:115)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:619)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:574)
at org.eclipse.equinox.launcher.Main.run(Main.java:1407)
at org.eclipse.equinox.launcher.Main.main(Main.java:1383)
Caused by: java.lang.IllegalArgumentException: Argument cannot be null
at org.eclipse.swt.SWT.error(SWT.java:4064)
at org.eclipse.swt.SWT.error(SWT.java:3998)
at org.eclipse.swt.SWT.error(SWT.java:3969)
at org.eclipse.swt.graphics.GC.setBackground(GC.java:3073)
at org.eclipse.bpel.common.ui.tray.TraySash$TrayTextureCanvas$1.paintControl(TraySash.java:71)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:223)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1258)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1282)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1267)
at org.eclipse.swt.widgets.Control.gtk_expose_event(Control.java:2781)
at org.eclipse.swt.widgets.Composite.gtk_expose_event(Composite.java:701)
at org.eclipse.swt.widgets.Canvas.gtk_expose_event(Canvas.java:167)
at org.eclipse.swt.widgets.Widget.windowProc(Widget.java:1739)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:4794)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:4372)
at org.eclipse.swt.internal.gtk.OS._gtk_main_do_event(Native Method)
at org.eclipse.swt.internal.gtk.OS.gtk_main_do_event(OS.java:8163)
at org.eclipse.swt.widgets.Display.eventProc(Display.java:1239)
at org.eclipse.swt.internal.gtk.OS._gdk_window_process_all_updates(Native Method)
at org.eclipse.swt.internal.gtk.OS.gdk_window_process_all_updates(OS.java:5327)
at org.eclipse.swt.widgets.Display.update(Display.java:4325)
at org.eclipse.ui.internal.LegacyAnimationFeedback.renderStep(LegacyAnimationFeedback.java:60)
at org.eclipse.ui.internal.AnimationEngine.updateDisplay(AnimationEngine.java:134)
at org.eclipse.ui.internal.AnimationEngine$1.run(AnimationEngine.java:122)
at org.eclipse.ui.internal.UILockListener.doPendingWork(UILockListener.java:164)
at org.eclipse.ui.internal.UISynchronizer$3.run(UISynchronizer.java:158)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:134)
... 23 more