I have followed these instructions below to upload a project.
Global setup:
Download and install Git git config --global user.name \"Your Name\"
Yes, It's a public key Problem. I'm a windows user,and the page below help me resolve this problem.
http://help.github.com/win-set-up-git/
more precisely this link should be helpful
https://help.github.com/articles/error-permission-denied-publickey