I've had a few problems with buyers, not sellers. I filed an "unpaid item case" with ebay. It took a week or so, but it was finally resolved with all eBay charges credited to me. I've never had to do this with any purchases that I've made, however. I'll bet that there is some means of recourse with your problem, too. Your question can probably be answered here: http://pages.ebay.com/help/policies/buyer-protection.html

Good luck,
Dave