Maps Crash after a rename

When I create a map, say level02 and then rename it to say level01.
If I then create a new map and call it level02, when I click on any map Unreal crashes. (I think you may have to exist and restart the editor)

It took me a many hours of painstakingly rolling back to a backup and rolling forward to figure this out.

I have not completely proven this, has anyone else experienced this?
Is this a defect?

Update:
After the rename (from level02 to level01) I created a new level00 and got the crash.
Maybe it has something to do with renaming a level.

Any help?

Thanks,
Guy.