If you’re experiencing odd behavior in Photoshop CS5, try resetting the program’s preferences to eliminate the possibility that the settings files have been corrupted. For me, this solved a problem with the Magic Wand Tool, which was selecting absolutely everything no matter how many settings I changed. I’ve also come across plugins causing the whole application to crash and shortcuts that cause the pane to freeze, so this is a good place to start debugging all sorts of issues.
Whilst holding down [Alt+Shift+Ctrl] open Photoshop CS5 from the programs menu. An alert window will ask if you want to delete the Photoshop settings file. Select Yes.
Whilst holding down [Shift+Option+Command] open Photoshop. An alert window will ask if you want to delete the Photoshop settings file. Select Yes.