Cant Join play on any server.

I can maintain on a server for about 20-30 sec then it says Disconnect, i have tried to use Repair, i have tried to reinstall, i have switched Internet to see if that was the problem, i cant get anything to work, its a real pain, so now im out of guesses on what can be wrong, so i want to hear what you have to say, i have btw also uninstalled Java, and installed it again, to see if it was that.