thanks!
funnily enough, the first thing i usually do with a mystery error message is paste it into google to see what it throws up. with this one i didnae bother as it seemed a bit vague. just goes to show you, there's nothing new under the sun.
anyway, for anyone else's interest, here's the short version.......
If you disconnect your Canon CanonScan LiDE 80, 50, or 30 scanner, be prepared for thousands of logfile entries while the scanner driver searches the USB bus for the scanner.
Looking for devices matching vendor ID=1193 and product ID=8717
Looking for devices matching vendor ID=1193 and product ID=8718
dumb canon scanner driver!
now i need to try and script sommit to disable the driver when i disconnect the scanner.