I have a problem with git on Windows Azure. Git status shows - \"fatal: bad object HEAD\" and I tried running:
git fsck --full
git gc
But
I solved this by copying the branch data (with the errors) to my apple laptop local git folder.
Somehow in the terminal and when running: git status, tells me more specific data where the error occurs. If you look under the errors, hopefully you see a list of folders with error. In my case GIT showed the folder which was responsible for the error. Deleting that folder and commiting the branche, I succeeded. git status was working again the other devices updating by git pull; everything working again on every machine.
Hopefully this will work for you also.