When you get below error from GitHub,

You can't push to git://github.com/user/repo.git
Use git@github.com:user/repo.git

and you are supposed to be the owner of that repo clone, you must have cloned (or checked out) the 'Public Clone URL' instead of 'Your Clone URL'. For me, the instant cure is to open .git/config file with editor and rewrite the url in [remote "origin"] entry.