Hi mate, instead of using WADUpdater use Easywad, its much easier and you totally know what;s going on. Just only use wad updater when you want to install pitcrews.
I've never had a problem with wad updater and that's my tool of choice. I think most problems which arise are to do with a corrupt file within the cars.wad. It's a bit unfair to just discredit Lo2k's tool completely.