The only advice I found in the few google pages was to switch of system restore then reboot then switch SS back on again. Avast! went off again this morning at 0953! Anyone else suffering this, or any ideas how to stop it?
In case anyone else gets this, I tracked it down to a programme called Wild Tangent - an on line gaming programme which AOL gave me for free when I downloaded their Instant Messenger 'AIM'. They didn't tell me it was there though! Guide to its removal is