First off. Sorry for the SEO opted title of this post, but I thought it could help someone to get an answer quickly instead of surfing the web for a 3 hours as I did. Solution where found at Superuser.
If you end up getting this message when you connect to GitHub after updating OSx Maverick 10.9.2, you probably have an old or conflicting certificate issued by DigiCert (you shouldn’t be allowed to access their page either if it’s a cert problem).
The solution is to remove the DigiCert (I had a bunch, wich I backed up before removing all of them) in your keychain access app, restart Crome and you should be good to go.