It's probably something odd about Photoshop that WB just can't handle, i.e., it doesn't act like a "normal" solitary rectangular window. It'd be nice if Stardock would post a list of apps that commonly need to be excluded somewhere on their site. Seems to me that there were some apps pre-installed in the exclusion list when I was using WB a while back, but you ought to be able to get an "automatic update" or a one-time warning ("This application may not be compatible with WindowBlinds") for known problem apps. Maybe that's too Microsoft-ish.