Uhhh . . . sounds like its reinstall time!

I know that doesn't sound like a good solution, but I've found that most of the time, errors of these sorts can't be worked out without a large amount of futzing. It's usually easier to just uninstall and reinstall.
If you do end up doing this, be sure to use the FS uninstall feature, as it will leave all of your addons alone and just erase everything the original disks installed. Saves a lot of retweaking and messing with little odd things!
