I teach at a college and we have Lightroom 2 installed on (recent model) iMacs. Adjusting the thumbnail slider does not change the size of the thumbnails. Also, in the Library, menus (i.e. folders/Collections) can't be collapsed.
Weird I know, but the same thing happened when we had Lightroom 1.
OS 10.5, about 20 machines.
Any suggestions welcome.