Installed PSE12 yesterday. It's slow and buggy. Locks up and freezes. Won't close when I click the X. My PSE11 runs smooth as silk. Do you have an update? I'm about to take my copy back to Costco if this doesn't get straightened out.
Have you created a new catalog in Elements 12 or converted your Elements 11 catalog to Elements 12 catalog? If it is a new catalog, has it completed generating thumbnails?
Also could you check your media analysis preferences and let us know which all analysis options are checked(go to Edit>Preferences>Media Analysis).