Peggy - This guy must be afraid of bidders not paying for more than one item. This is the sellers option and he might not have seen where he check a certain box when listing his items.
The seller might beable to change this but I don't know for sure. I have run into this same thing before but as you and I know its not a Ebay rule since we have both had the same bidder win more than one of our auctions.
Walt