I have: http://windows.github.com/
My current project has around 20k files, around 150MB (and not speaking about how slow it is and I cannot do a thing now) it doesn\'t
I am using windows client and getting the same error. Then suddenly I realized that my local db in app_data was opened on the SQL management. It just simply can't commit the some files to github if they are opened or using at the other programs.
Just disconnected management studio closed it and just simply committed.
This may be your case also. Check your files out!