Please provide more info. Is this when you try and join a lobby? Or enter your password? Sounds like it could be an issue with your account. If it's an issue with your account, you'll need to contact Uber – we can't help you on the forums. http://support.uberent.com/
Do you have any anti-virus installed? If yes, which one? Can you try to remove it and try again? PA.exe need to be allowed to make outbound connections to TCP ports 9000-9050 range.
I recently installed the game on a new computer, and I got that same error. I fixed it by deleting everything in the planetary annihilation folder but the launcher, then running the launcher and reinstalling the game.