Switching Application Focus from Adobe Photoshop CS5 to xScope
When I switch from a Photoshop document to xScope, my Photoshop window disappears. What's going on?
When using xScope 3 with Adobe Photoshop CS5, if you switch between your current document and an xScope tool, your Photoshop workspace will be pushed behind any other application windows you might have open. This is a result of the way that Photoshop sends messages to OS X when switching applications, and is not something we can currently fix.
Currently the best way to avoid this issue is by holding down the command key whenever interacting with an xScope window while working in Photoshop CS5. This prevents xScope from becoming the active window, but still allows you to interact with the tools.
An alternative solution to this is to keep an open Safari window with the "Top Sites" screen showing behind your Photoshop document. You can find out more information from Thibaut Sailly's blog post on the subject here.