After some investigation, we figured out the forum loading problem is not caused by the server any more. (It was server issue a while ago, but that problem should be fixed by now.)
We don't know what is causing the problem especially when I can't reproduce the problem on my side, so we will try updating the forum tonight from 3.6.2 to 3.6.5. The forum will be taken offline around 11pm or 12am tonight, PDT, but hopefully we can come back online in an hour or so.
Thank you for your patience!
Related thread: http://apforums.net/showthread.php?t=12210