This has been going on for a bit now and it is getting a little annoying.
When I am done with a particular forum I hit 'Mark forum as read' then go to another...after a while though...the forum comes up as having something new that I haven't seen but it didn't (and I checked for edits). I don't know if it is just due to were I am right now (at my parents place) or if this is a real glitch.