Adobe Creative Suite Cleaner Tool
In researching the problem, I came across several solutions that ranged from deleting a preference file to a complete uninstall and then reinstall. None of these options worked for me. In fact, once uninstalled, I was completely unable to successfully reinstall Photoshop while the rest of the suite worked just fine.
About to give up, I finally stumbled upon this support page at Adobe. The magical sounding "Adobe Create Suite Cleaner Tool".
And it worked!
I know there are a lot of frustrated people out there. Maybe it will work for you.