As an eBayer myself, I also ran into a couple of problems. But eBay helped
me take care of them, and both problems were resolved totally to my
satisfaction.

Here's what to do:

First, make sure you save all emails between you and the buyer. Then, use
the following URL to contact eBay to let them know about your problem:
http://pages.ebay.com/help/contact_inline/index.html

You will be expected to provide full copies (including headers) of all your
correspondence with the buyer. They will contact you very soon and work out
something in a day or two.

Don't give up! EBay wouldn't stay in business long if they weren't any good
at fraud elimination. You will win this. Just be diligent and patient.