Issue with Avira, Need help

I recently installed Avira Internet Security 2013 on my roomates PC and for some reason it is completely blocking access to the internet and I can't figure out why. The firewall settings are on the default setting so it doesn't seem to be that. It's strange. As soon as I uninstall it the internet works fine again. Does anybody have any idea what the issue could be? All of the free antivirus programs work fine on his PC.