I had this same problem. I don't know what fixed it, but I ran the setup/repair game option(during setup), and downloaded and installed the latest gamespy software. I don't know if the last thing has anything to do with the ingame browser, but one of those things seems to have helped.
The first time I ran into this problem was when I downloaded and installed the Command and Conquer Renegade demo and didn't install the gamespy software as I already had it. The demo wouldn't work and then I started to have those probs with MOHAA. Don't know if it's related.
Good Luck
------------------
