I recently upgraded from Photoshop 7 to 11 and now I'd finding that my photos have been automatically assigned additional and incorrect keyword tags. Most prevalent seems to be place and event mistagging. I'm now going back through all my photos to verify the correct tags and remove the incorrect.
Please follow the link I posted; they'll be able to help you better over there.
This is the forum for the full version of Photoshop, and it works differently.
Adobe has made the product naming confusing.