git error : Unable to write new index file

Hello all,

I have just started using git for a small project. I have
created empty repository using "git init" and it worked fine.
But after that when I have tried to add a file to the repository
using "git add <file_name>", I am getting the below error.

fatal: Unable to write new index file

The same error appears not only when adding files but also
whenever I add something (file, branch etc. ) to git repository.

I am using git on windows using cygwin and I have all permissions
(rwx) in the directory where I am running this command. Can anyone
please help me in resolving this issue ?

Thanks,
Mahesh