Cannot add derby nature to project
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I am having troubles adding ( and removing) derby nature to my projects. I did menage to add and run derby in one of my projects but now I cant add it to any new ones ( dynamic web project or java). I am getting this error:  
"Error adding Derby jars to the project 'web222' : java.lang.ClassCastException: org.eclipse.ui.internal.WorkbenchWindow cannot be cast to org.eclipse.jface.window.ApplicationWindow"
I am using new eclipse juno ee. What am I doing wrong? 
Thanks in advence..