It can and is one of them, and I guarantee that, at the very least, logging on with Firefox will work for you. (;
SWC has a server-side problem preventing some accounts from logging on with IE. This seems to selectively affect certain accounts due to how the password is recognized by the server (or something.. I'm not a programmer, but you get the idea), and Firefox users do not encounter this problem at all. One of the programmers was able to track down the cause of it, but unfortunately no solution has been found.