Why won't my printer print?

[chakka16]

Help, somebody, please. I'm going mad. I bought a Canon MP390 multi-functional device (fax, photocopier, photoprinter, printer, scanner) which has been thoroughly tested by local computer engineers and given a clean bill of health. It works fine on those tasks where the computer is not involved (fax, photoprinter, photocopier) but it simply will not print from my computer or scan to it. The drivers are properly installed and recognised by the computer, as is the machine itself in Device Manager. Everything checks out, but when I try to print I get the message 'Printer does not respond'. I have tried all my USB ports in turn, with no effect. I eventually decided that the problem lay with my Windows ME OS which was beginning to wilt anyway, so I invested in Windows XP. It makes no difference. Anyone got any ideas? Canon haven't.