Have you tried to contact this person through the eBay contact facility?
Might be worth one last shot at it to see if they have a phone number listed to give them a call and find out what's going on.
Did any of the other sellers have any more contact info which they would be willing to share with you?
Seriously though, I think you will have to end the auction and block them from bidding on your auctions in future, as they're a waste of time.

That's my ten penn'orth!
