10.7 freezes whenever screen saver activates!!

Installed Lion. Upgraded all 30,000 of my photos as per screen prompts. Now unable to use my Mac ANY time screen saver activates. It freezes, hangs, crashes. NEVER had any of these problems with 10.6 and, because I've "upgraded" my entire iPhoto Library (as per screen prompts) I am STUCK with this new OS!!!!!!!!!!!!!!!!

How can I "de-upgrade" my iPhoto library so I can revert to a system that functions??????

This is ONE lion that should have been kept in its cage.