Vista Mouse & Keyboard not detected after Idle

My office is having issues with their newly updated systems. We have
installed Vista on all of our machines. When anyone leaves their
computer for an extended period of time, Vista will automatically log
that user out. When the user returns to their computer, the mouse and
keyboard are not detected. We have to do hard reboots to get everything
connected again.

Any ideas as to how to solve this? Thank you!