Well, Dotsie, so far I haven't been able to figure out any particular rhyme or reason - and cannot reproduce the problem (your techies may want to know that last bit). I cannot MAKE the Active Topics not work.

Sometimes I can flip back and forth [between Active Topics and the various posts] as often as I want to - for hours at a time. Other times, I only flip back and forth a couple of times and then get that message about it being unavailable. I've tried Chick's solution (clicking on Search Results instead (when the Active Topics is unavailable), but that doesn't work for me.

Earlier this afternoon, I had problems with Active Topics after being on for only five minutes. Tonight I don't (so far) and I've already been browsing various threads here for about 30 minutes.

It's not that it's inconvenient (although it's frustrating when there are dozens of new posts I'm trying to read and I keep getting locked out of the Active Topics page), it's the inconsistency that's baffling for me. As a former techie, that inconsistency alone would make it something I'd want to troubleshoot.