It's not down. DBG did some server maintenance yesterday and messed something up with the login process.
Some people flushed their DNS, but the PSForever.net launcher bypassed this problem for me. You can download it here:
http://files.psforever.net/releases/...er_1.0.0.4.zip
Make sure to extract both files together, then run the executable. Point it to your PlanetSide directory, and check "Skip Launcher." When you get in the game client, you should be prompted for your username and password.
Enjoy!