The USB action of the tethered camera just doesnt wake the computer from the screen saver. (its not actually asleep- just on screen saver mode). Almost anything else connected..Ie. mouse, bluetooth mouse, scanner, trackpad, etc.) will wake it out of screen saver mode EXCEPT the tethered SLR...
I have a tethering camera shooting situation where I want my nikon d200 (but i imagine the camera itself does not matter) connected via USB to shoot images to a tethering app, which it does perfectly (Ive used nikon camera control pro and SmartShooter App), display the image (does this too) and...