I have been having problems with a Canon I350 on a sony vaio running XP Professional – it keeps disconnecting and saying the printer is offline – even when it is clearly online. After checking all the connections no problem was apparent.
After further investigation it seems that the only solution is to delete the printer from the printers menu (found in the control panel). Then reinstall the printer following the insructions found on the canon website. But in a nut shell, all you do is load the printer drivers (found here) and when they are installed simply plug in the printer.
Once this is done the printer will work again….if you have any problems with this – leave a comment and I will see if I can help!