So I close the project MyApp, then from the OS delete the MyApp directory: the IDE immediately gets an AssertionError - why? details below: java.lang.AssertionError: java.io.FileNotFoundException: C:\Documents and Settings\David\MyApp\nbproject\project.xml (The system cannot find the path specified) at org.netbeans.spi.project.support.ant.SourcesHelper.getProject(SourcesHelper.java:198) at org.netbeans.spi.project.support.ant.SourcesHelper.access$200(SourcesHelper.java:55) at org.netbeans.spi.project.support.ant.SourcesHelper$SourceRoot.toGroup(SourcesHelper.java:83) at org.netbeans.spi.project.support.ant.SourcesHelper$SourcesImpl.getSourceGroups(SourcesHelper.java:440) at org.netbeans.modules.java.j2seproject.ui.J2SEPhysicalViewProvider$LogicalViewChildren.getKeys(J2SEPhysicalViewProvider.java:316) at org.netbeans.modules.java.j2seproject.ui.J2SEPhysicalViewProvider$LogicalViewChildren.stateChanged(J2SEPhysicalViewProvider.java:309) at org.netbeans.spi.project.support.ant.SourcesHelper$SourcesImpl.fireChange(SourcesHelper.java:475) at org.netbeans.spi.project.support.ant.SourcesHelper$SourcesImpl.fileDeleted(SourcesHelper.java:486) at org.netbeans.modules.project.ant.FileChangeSupport$Holder.someChange(FileChangeSupport.java:145) at org.netbeans.modules.project.ant.FileChangeSupport$Holder.fileDeleted(FileChangeSupport.java:158) at org.openide.filesystems.FCLSupport.dispatchEvent(FCLSupport.java:78) at org.openide.filesystems.FileObject$ED.dispatch(FileObject.java:764) at org.openide.filesystems.FileSystem$EventDispatcher.run(FileSystem.java:755) at org.openide.filesystems.EventControl.dispatchEvent(EventControl.java:47) at org.openide.filesystems.FileSystem.dispatchEvent(FileSystem.java:468) at org.openide.filesystems.FileObject.dispatchEvent(FileObject.java:405) at org.openide.filesystems.FileObject.fireFileDeletedEvent(FileObject.java:378) at org.netbeans.modules.masterfs.MasterFileObject.access$800(MasterFileObject.java:34) at org.netbeans.modules.masterfs.MasterFileObject$FileChangeListenerImpl.fileDeleted(MasterFileObject.java:762) at org.openide.filesystems.FCLSupport.dispatchEvent(FCLSupport.java:78) at org.openide.filesystems.FileObject$ED.dispatch(FileObject.java:764) at org.openide.filesystems.EventControl.invokeDispatchers(EventControl.java:160) at org.openide.filesystems.EventControl.exitAtomicAction(EventControl.java:138) at org.openide.filesystems.EventControl.finishAtomicAction(EventControl.java:79) at org.openide.filesystems.FileSystem.finishAtomicAction(FileSystem.java:458) at org.openide.filesystems.AbstractFileObject.refresh(AbstractFileObject.java:747) at org.openide.filesystems.AbstractFileObject.refresh(AbstractFileObject.java:679) at org.openide.filesystems.AbstractFolder.refresh(AbstractFolder.java:393) at org.openide.filesystems.AbstractFileSystem.refresh(AbstractFileSystem.java:80) at org.netbeans.modules.masterfs.MasterFileSystem.refresh(MasterFileSystem.java:136) at org.netbeans.modules.java.j2seproject.J2SEProjectGenerator.refreshFileSystem(J2SEProjectGenerator.java:249) at org.netbeans.modules.java.j2seproject.J2SEProjectGenerator.createProjectDir(J2SEProjectGenerator.java:196) at org.netbeans.modules.java.j2seproject.J2SEProjectGenerator.createProject(J2SEProjectGenerator.java:56) at org.netbeans.modules.java.j2seproject.ui.wizards.NewJ2SEProjectWizardIterator.instantiate(NewJ2SEProjectWizardIterator.java:111) at org.openide.loaders.TemplateWizard$Brigde2Iterator.instantiate(TemplateWizard.java:957) at org.openide.loaders.TemplateWizard.handleInstantiate(TemplateWizard.java:549) at org.openide.loaders.TemplateWizard.instantiateImpl(TemplateWizard.java:465) at org.openide.loaders.TemplateWizard.instantiate(TemplateWizard.java:351) at org.netbeans.modules.project.ui.actions.NewProject.actionPerformed(NewProject.java:75) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1786) at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1839) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258) at javax.swing.AbstractButton.doClick(AbstractButton.java:289) at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1113) at javax.swing.plaf.basic.BasicMenuItemUI$MouseInputHandler.mouseReleased(BasicMenuItemUI.java:943) at java.awt.Component.processMouseEvent(Component.java:5100) at java.awt.Component.processEvent(Component.java:4897) at java.awt.Container.processEvent(Container.java:1569) at java.awt.Component.dispatchEventImpl(Component.java:3615) at java.awt.Container.dispatchEventImpl(Container.java:1627) at java.awt.Component.dispatchEvent(Component.java:3477) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128) at java.awt.Container.dispatchEventImpl(Container.java:1613) at java.awt.Window.dispatchEventImpl(Window.java:1606) at java.awt.Component.dispatchEvent(Component.java:3477) at java.awt.EventQueue.dispatchEvent(EventQueue.java:456) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137) at java.awt.EventDispatchThread.run(EventDispatchThread.java:100) Caused by: java.io.FileNotFoundException: C:\Documents and Settings\David\MyApp\nbproject\project.xml (The system cannot find the path specified) at java.io.FileInputStream.open(Native Method) at java.io.FileInputStream.(FileInputStream.java:106) at java.io.FileInputStream.(FileInputStream.java:66) at sun.net.www.protocol.file.FileURLConnection.connect(FileURLConnection.java:69) at sun.net.www.protocol.file.FileURLConnection.getInputStream(FileURLConnection.java:156) at org.apache.xerces.impl.XMLEntityManager.setupCurrentEntity(Unknown Source) at org.apache.xerces.impl.XMLVersionDetector.determineDocVersion(Unknown Source) at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source) at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source) at org.apache.xerces.parsers.XMLParser.parse(Unknown Source) at org.apache.xerces.parsers.DOMParser.parse(Unknown Source) at org.apache.xerces.jaxp.DocumentBuilderImpl.parse(Unknown Source) at org.openide.xml.XMLUtil.parse(XMLUtil.java:283) at org.netbeans.modules.project.ant.AntBasedProjectFactorySingleton.loadProject(AntBasedProjectFactorySingleton.java:109) at org.netbeans.api.project.ProjectManager.createProject(ProjectManager.java:254) at org.netbeans.api.project.ProjectManager.access$500(ProjectManager.java:41) at org.netbeans.api.project.ProjectManager$2.run(ProjectManager.java:205) at org.openide.util.Mutex.readAccess(Mutex.java:208) at org.netbeans.api.project.ProjectManager.findProject(ProjectManager.java:170) at org.netbeans.spi.project.support.ant.SourcesHelper.getProject(SourcesHelper.java:194) [catch] ... 63 more