I know that with some printers they will not work when either of the cartridges is empty but I am not sure if this applies to the Canon.
The owner tells me that it has worked when the colour cartridge is empty and the black is ok.
At the moment it will not print, I have reloaded the drivers and tried it on another pc but to no avail. The software suggests that the colour cartridge is empty. I have checked on the Canon website but no useful info was present.

Have you pulled both cartridges and checked their levels, and also made sure they are securely mounted? (I know, sounds silly, but I've overlooked those two items myself)...

Yep, those cartridges have been in and out many times to try and cure the problem.

hmmm not to sure, but i think the same applys to Cannon printers. tho you could try setting to mono printing only and see if it will print using just the black cart, it may work, tho i think it will be like other printers in having to get the colour cart replaced before it will.

I have an older BJC-4100, and it doesn't care whether there's ink in the cartridges or not, so I would be looking for another problem.
If you're using the dual cartridge head, i.e. a small black cartridge and a color cartridge, you might try replacing the print head assembly. A new one comes with both cartridges.
HTH,
Strider