If you're trying to update/connect and experiencing this problem right now, try again later. The server has been down for a little over an hour and there has been no info on when it will be back up.This is just speculation, but if you have corrupted .dat files due to the update server dropping in the middle of an update or something similar happened, then you may need to do a fresh install and fresh update to fix your problem.
From what I've experienced, this is the screen you see the first time you run the client. It usually says "PRESS ENTER" where you typed in your username. Once again this is speculation based on my experiences with the game/client to date. Regardless if it's garbage symbols, "PRESS ENTER", or something you typed in the field -- I'm pretty sure you still need to press enter here to get past that screen. The most likely reason you're not getting past this screen is because the server is not up. (Just a guess... ) Once the server is back up, you -should- be able to press enter and get to usual login screen to input your account information in the proper username/password fields.If the problem persists once the server is back up, try what I suggested before and do a clean install/update of the client.