I thought I saw something about this, but I can't seem to find it.
My app loses focus after the screen saver activates. If I remember correctly, after pressing a key, my app screen does show up. However, I'm unable to control my app. The only thing I can do is press the home key, and exit all the way out.
If it makes any difference, I have a posterboard screen, which goes to a springboard screen, which goes to an imagecanvas...
My issue ended up being that I had an "roOneLineDialog" with ShowBusyAnimation() open earlier in the stack, and apparently it was capturing focus (without repainting) after exiting the screensaver. If you have any dialogs with ShowBusyAnimation() enabled, you'll want to make sure you close and kill the reference before painting a new screen on top of them.