Here'e the story -- I own LR3. I downloaded the trial version of CS6. I did not keep CS6, but instead deleted it. I bought CS5 (yes, licensed). When I'm in LR3 and I attempt to "Edit in..." via the pulldown menu, LR3 will not give me the option to edit in CS5. It does, however, give me the "option" to edit in CS6, although CS6 is no longer existent. How can I get LR3 to recognize CS5 at the pulldown menu for Photo>Edit in...?
Please keep in mind that both applications are working correctly independent of one another.
In Lightroom - Preferences, External Editing, should let you choose the program you are going to use. Just checked mine and it said CS2, but I know I am at CS4.
This allows you to find an exe file and tell Lightroom to add that to the list. So, find photoshop.exe in the CS5 program folder and it will be in the drop down