The commit button just pops up a menu with some options. Create patch is the only one that does anything.
This is on Mac OS 10.8.2 with Git 220.127.116.11 from homebrew.
See http://cl.ly/3w2n1W3L0f3C for video.
Could you please attach the log file (Help -> Reveal Log in Finder)?
It looks like RM has some problems with caches Try File|Invalidate Caches...
That did it. Thanks!