I hit Mark All Read in my view new posts/all page and they don't get marked read. I'm using Chrome but I tested it in firefox and it's not working there either. It IS working when I go to the individual forums and mark them all read there.
Mine was acting up a few days ago as well. When clicking Mark Read on any page it would load me up to the Message Centre (even if I was on RPG Centre or Question Centre) and nothing is marked read when going back.