If IntelliJ hangs at startup, taking forever showing a status of "Saving Local History" but not using any CPU time, the problem may just be a corrupt cache. I've seen this a couple of times in the last year.

The fix is to delete the version control cache directory.

On Mac OS X, it's located here:

~/Library/Caches/IntelliJ IDEA/vcs/

On Windows, it's located here:

~/.IntelliJIdea/system/vcs/

(where by "~" I mean C:\Documents and Settings\<your user name> )