If the installer says there's no internet connection available, since its runs on two mirrors at the same time, it's highly unlikely they would be both offline at the same time. And they aren't anyway.
It must be some security program you have installed that is blocking online access to the installer. Turn off every security software like antivirus, antispyware, and if you have a firewall, configure it to grant online access to the Couatl_updater program in the fsdreamteam\Coautl folder, if you were trying to do Live Update.