eclipse plugin: Widgetset compilation failed


I am using the eclipse-plugin in eclipse Helios EE version. When trying to compile the widgetssets I get a stacktrace: zip file closed (see below).
Alas it is not stated which zip file is closed so I have no clue where to look.
Anybody have the same problem or a workaround? Help is needed as I am totally stuck right now, cannot continu developing : (

I had the same error once directly after installing the eclipse plugin, but a restart of eclipse fixed it. Now that does not help, even restarting windows does not help.

Regards, Rob van der Veer.

java.lang.IllegalStateException: zip file closed
at java.util.jar.JarFile.entries(
at com.vaadin.integration.eclipse.util.WidgetsetUtil.isNeededForWidgetsetCompilation(
at com.vaadin.integration.eclipse.util.WidgetsetUtil.getAvailableVaadinWidgetsetPackages(
at com.vaadin.integration.eclipse.util.WidgetsetUtil.compileWidgetset(
at com.vaadin.integration.eclipse.builder.WidgetsetBuildManager.compileWidgetsetIfNotRunning(
at com.vaadin.integration.eclipse.builder.WidgetsetBuildManager.compileWidgetsets(
at com.vaadin.integration.eclipse.handlers.CompileWidgetsetHandler$1.compileFile(
at com.vaadin.integration.eclipse.handlers.CompileWidgetsetHandler$

vaadin version: 6.6.2 and 6.6.4


I installed the newest eclipse (3.7 indigo) and a reinstalled the vaadin plugin and somehow compiling works again.