As many of you have reported, there are links that aren't working. This can be cause by 2 different bugs.
If you have an old link and it's taking you to a blank board, or a page-not-found, try those links again. We pushed a code fix for a ton of redirects on old links yesterday. Today, I'm getting a lot of emails and PMs saying that our members' old links are working now! If your old links aren't redirecting yet, let's give it a few more days. These new redirects are cached, and are only cleared once a day. After the cache clears, the redirects render. Most if not all of these should be working next week!
"Unexpected Error" pages
If you click on a link and you get this Error page, this is a page-loading problem related to the Visitor (not verified) bug. The tech team is working on this bug as we speak; it's a top priority. (See my Message Board Fixes - Updates  thread for a full explanation of what causes this.)
UPDATE: Most of the Error pages related to the Visitor status have been fixed. We know there are some pages that still don't load, but we'll need to look at these on a case-by-case basis. We're making progress! :)