did you pay via credit card through Paypal? If so, contact your credit card company stat to reverse the charges. If you paid through a bank account, try contacting your bank to see if they'll do anything.
Is the seller still selling on ebay?
Keep on pressing. You'll have to rant and rave, it seems, in this situation. File mail fraud claims against them. If you go over to the ebay discussion boards you'll find or can be directed to if you ask, one of several threads that lists everything you can do.
When they're being investigated by the gov't for mail fraud, sometimes a refund will come quickly
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