Product Version = NetBeans IDE 7.0 (Build 201104080000)
Operating System = Windows XP version 5.1 running on x86
Java; VM; Vendor = 1.6.0_18
Runtime = Java HotSpot(TM) Client VM 16.0-b13

The project was compiling and running just fine. Then a imported the project into a subversion repository. I can build the project without any error, but then when I want to run it I get a NoClassDeftFoundError exception for the main class. Then I try to deleted manually the "build" directory of the project. But it doesn't solve the issue. I try this a few times, and then all the classes in the project show a red dot with an exclamation mark: the ide  tells me they are all duplicates, which is actually not the case.

Then I close netbeans 7.0 and reopens the same project with netbeans 6.9, and everything works smoothly. no "duplicate class" eror, no "NoClassDefFoundError" exceptoin. 

Then I close netbeans 6.9 and reopens the same project with netbean 7.0, but the "duplicate class" errors are back.

I have uninstalled the CVS, Subvsersion and Local History plugins from netbeans 7.0, but the errors are still there.