I have had a couple problems in the past, but nothing that I couldn't fix without having to do a full re-install. I have my folders backed up as well. I simply run launch from my "main" wow install and just copy the patched files over to my other folders (I don't copy any folders within the wow folder, just the files). Haven't had any issues with the last few patches.

So, you probably just don't have your set up the way you need to for multiboxing. I don't know. Anyway, Blizzard doesn't really make it that easy though. Why they changed the folders on Vista is beyond me. Put the patch files in the main folder damnit!!

As for other games. I like Vanguard Saga of Heroes. I played Everquest for a long time so it seemed like what EQ2 should have been. My brother got bored of WoW and has been playing Vanguard for about a year. I'd give that a shot, especially if you used to play EQ.