My private message settings - among other things - seems to revert to older readings. After I've gone through my inbox I may suddenly see a bold Unread "2" or "3". When I go to the inbox it turns out that they are old messages that I've already read. Why do they keep marking themselves as unread? Windows XP & Opera. No spyware/adware/malware. Not a major issue - just wanted to provide some feedback. It may be the Opera wot's doin' it.
Hmmm... what's the timestamp at the bottom of the page? The only thing I can think of would be your browser caching the pages improperly.
Sounds like caching to me... if you go to UserCP and do a hard reload (or even flush your browser's cache). Maybe Opera is ignoring the nocache directives the forum sends for some reason.
It looks like each time I return the User CP is stuck in the time of the last visit and requires a hard refresh.
Unfortunately there isn't a whole lot I can do about it on this end. Your browser is ignoring the no cache directives in the HTTP headers the forum is sending.