GitHub - HTTPS access

As you did saw yourself in GitHub support, Scott Schacon himself suggested:

So I guess your .netrc is incorrect or something?
Try removing the info from your .netrc and cloning first (since it's a public repo).

If it isn't a GitHub server issue, it could be your firewall.
And/or your proxy (git config --global http.proxy http://user:password@proxy:xxx).

Just to add to this discussion, for some reason or another, it seems to work for me when I use http rather than https.