Attempted to import a very simple Jbuilder 2006 project.

I did the following:-
1. Installed JBuilder Project Importer module.
2. Uninstalled Eclipse Project Importer module.
3. Browsed to and selected jpx file for project to import.
4. Selected a destination Folder
5. Clicked Finish
6. 'Importing selected projects' progress bar reached 20%, then threw the following exception:-

java.lang.IllegalStateException: Cannot generate build scripts from a modified project
	at org.netbeans.spi.project.support.ant.GeneratedFilesHelper$2.run(GeneratedFilesHelper.java:559)
	at org.netbeans.spi.project.support.ant.GeneratedFilesHelper$2.run(GeneratedFilesHelper.java:557)
	at org.openide.util.Mutex.readAccess(Mutex.java:327)
	at org.netbeans.spi.project.support.ant.GeneratedFilesHelper.getBuildScriptState(GeneratedFilesHelper.java:556)
	at org.netbeans.spi.project.support.ant.GeneratedFilesHelper$3.run(GeneratedFilesHelper.java:773)
	at org.netbeans.spi.project.support.ant.GeneratedFilesHelper$3.run(GeneratedFilesHelper.java:772)
	at org.openide.util.Mutex.writeAccess(Mutex.java:433)
	at org.netbeans.spi.project.support.ant.GeneratedFilesHelper.refreshBuildScript(GeneratedFilesHelper.java:771)
	at org.netbeans.modules.java.j2seproject.J2SEProject$ProjectOpenedHookImpl.projectOpened(J2SEProject.java:484)
	at org.netbeans.spi.project.ui.ProjectOpenedHook$1.projectOpened(ProjectOpenedHook.java:81)
	at org.netbeans.spi.project.ui.support.UILookupMergerSupport$OpenHookImpl.projectOpened
(UILookupMergerSupport.java:193)
	at org.netbeans.spi.project.ui.ProjectOpenedHook$1.projectOpened(ProjectOpenedHook.java:81)
	at org.netbeans.modules.project.ui.OpenProjectList.notifyOpened(OpenProjectList.java:1003)
	at org.netbeans.modules.project.ui.OpenProjectList.doOpenProject(OpenProjectList.java:1051)
	at org.netbeans.modules.project.ui.OpenProjectList.doOpen(OpenProjectList.java:615)
	at org.netbeans.modules.project.ui.OpenProjectList.open(OpenProjectList.java:528)
	at org.netbeans.modules.project.ui.OpenProjectList.open(OpenProjectList.java:464)
	at org.netbeans.modules.project.ui.OpenProjectList.open(OpenProjectList.java:460)
	at org.netbeans.modules.project.ui.OpenProjectsTrampolineImpl.openAPI(OpenProjectsTrampolineImpl.java:71)
	at org.netbeans.api.project.ui.OpenProjects.open(OpenProjects.java:169)
	at org.netbeans.modules.projectimport.jbuilder.ImportAction.performImport(ImportAction.java:100)
	at org.netbeans.modules.projectimport.jbuilder.ImportAction.performAction(ImportAction.java:75)
	at org.openide.util.actions.CallableSystemAction$1.run(CallableSystemAction.java:118)
	at org.netbeans.modules.openide.util.ActionsBridge.doPerformAction(ActionsBridge.java:77)
	at org.openide.util.actions.CallableSystemAction.actionPerformed(CallableSystemAction.java:114)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
	at javax.swing.AbstractButton.doClick(AbstractButton.java:357)
	at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1220)
	at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:1261)
	at java.awt.Component.processMouseEvent(Component.java:6041)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
	at java.awt.Component.processEvent(Component.java:5806)
	at java.awt.Container.processEvent(Container.java:2058)
	at java.awt.Component.dispatchEventImpl(Component.java:4413)
	at java.awt.Container.dispatchEventImpl(Container.java:2116)
	at java.awt.Component.dispatchEvent(Component.java:4243)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
	at java.awt.Container.dispatchEventImpl(Container.java:2102)
	at java.awt.Window.dispatchEventImpl(Window.java:2440)
	at java.awt.Component.dispatchEvent(Component.java:4243)
[catch] at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
	at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)


The project in question had only one class in it and this is it:-

public class class1
{
  public class1()
  {
    int a = 0;

    a++;
  }
}

I have only recently installed NB6.5 (Build 200811100001, Java:1.6.0_05; Java HotSpot(TM) Client VM 10.0-b19 ) and in 
all other regards it is behaving fine.