[Geoff Winnington-Ball (RIP)]

To my knowledge, they're very good about this stuff. Write them with proof that the images have been stolen and request that the auctions be closed and the seller be removed.

Next, write the owner of that website and hint that your agents are compiling evidence for legal action against him for theft of property, but if your images are withdrawn, you will cease and desist.

Lastly, Hanno is right - you have to assert some sort of 'watermark' on the stuff you display. BTW, there are also a few javascript programs out there which will prevent right-clicking and saving - not a conclusive answer, but one which will at least stall casual theft.

Good luck and keep us posted.