I could have sworn I did that before. Maybe I added it then deleted the wrong one....
But why would my old bookmark still bring me to the Community Discussion page, then after I sign in, I get the message?
As I said in my edit (wasn't fast enough) they had soft links (symbolic links) in place after the changes to keep -some- level of compatibility with existing links. After the change links to specific threads would instead go to the subforum's first page, but with a deformed URL (IIRC). After you log in, the log in tries to take you back to the page you were originally viewing and the forum doesn't know where that page is anymore, as it can't find the location.
Granted, I could be completely off base, but that is the only logical conclusion I can reach for the problem.
Change your bookmark to this: http://www.gamesas.com/index.php?/forum/18-community-discussion/ and see if it still happens. Maybe call it Community Discussion 2.0 so you don't get it confused with the old one (or just edit the old one)