Ok.. Certainly worth following the advice given and checking what has been recommended..BUT..
to add to the clamour.. TCPVIEW.. this gives you ports to process information.. it would be interesting to see a log from that..

When the windows closes or the startmenu opens.. is there mouse activity? i mean mouse movement not from your input..
if not.. Try a new Keyboard.. I chased a virus in a machine for best part of a day only to find a electricly stuck key and two intermittantly stuck keys .. this resulted in some movement trigering screen activity, some functions unavailable, certain functions didn't work.. the keys involved, ALT, Windows, up arrow..

It is a thought