Though it isn't my place to say, or give advice, usually when forums do not let you log in, you need to clear your cookies, and then it should let you.
I believe you're using Internet Explorer, I havn't used that in awhile, so I cannot rememember how to clear the cookies. I believe you go to Tools, and then Internet Options. It should be on one of the Tabs, to clear your cookies. This will also reset all your passwords, so, if you want too, be careful. You can also go to your temporary internet files, fine the exact cookie, and delete that, but that will be harder to do.
This information is all based on if it is, indeed, the cookies causing the error.
