The Preferences file is where Photoshop stores many of its performance settings. It means that the Preferences file has been damaged and the information inside of it is messed up. I don't mean it's been accepting bribes from shady business associates (or at least, we haven't found anyone willing to talk). Is your copy of Photoshop acting strange? Panels or menu items disappearing? Tools misbehaving? Chances are, the problem is that your Photoshop Preferences file has become corrupted.
