We're sorry but a serious error has occurred in the system.
If this happens to you, I have a possible quick solution (if you just want to get to the page in question):
Use your browser's menu option to have it create a "new private window" (FireFox), or "new incognito Window" (Chrome), or "new session" (IE), or the like.
This will open a new window for your browser, and it will NOT send any cookies to the page in question. And you should find that suddenly the forums "work", which tells you that the problem was about the server's unhappiness with something about the cookies in your browser.
If that's enough, great. If you want to know a bit more, read on.