I posted a fix for this a while back. Either it works or I'm flashing the right ROM's lol.
http://forum.ppcgeeks.com/showthread...hlight=777+fix
It's not that your connection settings are bad. It would happen to me mainly after receiving a phone call while I was using data. You have to install Sdkcerts along with the cab or you will get a message ...untrusted source.. instead of the unable to connect #777 one,