I think I see what's going on---if I go to "My Forums" , and then go down to a forum and select it, I then get the message in the top right hand side that allows me to mark all post read in that particular forum--which is cool. When I go to "My Forums" and then select "Posts since Last Visit" (which is the way I use the forum section), the "Mark Forums Read" action is not there.
I'm looking for the line at the bottom of each forum page that allowed me to mark all of MY forums read, no matter what page I'm on or forum I'm in.
Not a big deal, but I got a little bit spoiled with the convenience of that feature. Unless I'm wrong, the only way to do that now is to go back to the "Forum Home" page, and click on "Mark all Forums Read" there.