Did you try using the repair utility for WoW? I had this problem when I was using Jamba 0.5 and Innerspace. Lots of things would cause issues, going into combat, someone dying, zone loading, any mob dying, mob aggroing, the list goes on. I reverted back to 0.4 and everything is fine. If that doesnt fix it, maybe you need to reinstall WoW. I hate doing it too, but sometimes the repair utility doesnt catch corrupted files.