I am assuming you're not 2-boxing or doing anything that is explicitly against the rules. That said, sometimes the error you're seeing is just a fluke and will resolve itself after waiting a couple of minutes.
However, if it does not then you'll need to post (politely I might add) in the petitions forums, explaining what you're seeing when you try to login, and the situation as you see it.
http://www.project1999.org/forums/forumdisplay.php?f=25
Good luck!