I'm a total newb with git and was following some installation instruction on a website and was getting the permission denied (publickey) error.
I followed the instructions to generate the RSA key pairs (ssh-keygen -t rsa). This worked fine but I was still getting the error. What I did not realize was that you have to actually go the the GIT website (github.com), register and enter that key on their website.
I hope this helps out another poor newb out there.
Cheers!