This is pretty maddening as I wanted to stop using gimp. I have tried reinstalling LR4 but still all the Photoshop options are greyed out when I want to edit a pic; and even trying to add PSE 10 manually as an external editor does nothing.
I purchased PSE 10 via the Apple App Store. The Application folder shows the actual PSE 10 program (i.e. it's not the "link to Support Files/PSE10" problem). I'm pretty good with computers but this one has stumped me. One Adobe product seems to hate another Adobe product! ;-)