Sorry, thought it would just be an option I needed to tick somewhere.
Samsung ML1510 laser printer, 6 months old, drivers as came with it, listed as Samsung 1510_700 Series. 900 Celeron, 384mb RAM, Windows XP Professional. Haven't installed SP2 due to the consensus of opinion hardly being unanimous. If it ain't broke, etc......
This only started happening after I installed XP over 98SE, but whether it's developed since then or would have happened immediately afterwards I don't know. Don't need to reboot as often with XP as I used to!