You know what it might be...if you have it so the first post shows up first instead of last post first, you'll have to scroll down a ways in longer forums to see if anyone has added anything new. To change this, so the newer posts show up at the top, simply go to your profile, and change the "preferred message ordering" to whichever way you would prefer. Putting the last post first will make the newest post show up on top. I like it that way better, less work for my finger and mouse.

Good luck!
Let me know if this helps!