This bug was originally marked as duplicate of bug 204849, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.

Build: NetBeans IDE Dev (Build 201203280401)
VM: Java HotSpot(TM) Client VM, 22.1-b02, Java(TM) SE Runtime Environment, 1.7.0_03-b05
OS: Windows Vista

User Comments:
MackSix: Exception Reporter Test

GUEST: I renamed a project including the project directory name with Netbeans

GUEST: twice rename project

MackSix: Renamed project with renaming of folder. Renamed package. The project only has 1 package. The right clicked on project and chose "Run" and got this exception.

The Output window also says, Error: Could not find or load main class observer_243.Main

"observer_243" is what I renamed the package too.

GUEST: Compiling project

greggwon: Just building the current project.  background processing probably got caught with it's hand in the cookie jar, mucking with stuff and slowing down the build.

MackSix: This still occurs. Rename Project wih folder option then rename Package with refactor option and then try to run the project. Also, the output window says: Error: Could not find or load main class javaapplication12.JavaApplication1
Java Result: 1

MackSix: 7.1 RC1 - Had already changed the name of the Project with Folder and Package with refactoring a couple of times. Did it again and this happened.

MackSix: Renaming project and project folder in the Projects window.

GUEST: editing a class

GUEST: renaming a project that had the same name as another open project

MackSix: Went through the proceedure again with project that ran ok before renaming Project and Package.

GUEST: Renamed a newly created EE Client.

GUEST: Renombrando un proyecto

GUEST: Went to exit an application that had thrown an out of memory error.

MackSix: Renamed Java Package.
Correction: Renamed Java Project.

MackSix: This bug still occurs. Renaming a project with folder.

sunbiz: Renaming a JavaCard project does not work correct. It throws the exception when renaming a project and its folder

GUEST: renaming a project




Stacktrace: 
java.lang.AssertionError: If valid, it should be a folder: C:\Users\Mark\Documents\NetBeansProjects\JavaApplication28\build\classes\javaapplication28@4e32eb7:1e857d8
   at org.netbeans.modules.masterfs.watcher.Watcher$Ext.unregister(Watcher.java:248)
   at org.netbeans.modules.masterfs.watcher.Watcher.unregister(Watcher.java:127)
   at org.netbeans.modules.masterfs.filebasedfs.fileobjects.BaseFileObj.removeFileChangeListener(BaseFileObj.java:519)
   at org.openide.filesystems.FileUtil$Holder.locateCurrent(FileUtil.java:441)
   at org.openide.filesystems.FileUtil$Holder.someChange(FileUtil.java:461)
   at org.openide.filesystems.FileUtil$Holder.fileDeleted(FileUtil.java:500)