Well, I'd say "Congratulations" actually. Ebay is a very serious market place, and auctions do have the actually legal consequence of bying and selling for a certain price. The dealer has no right to simply terminate the auction because they were hoping for more profit.
I recommend that you contact them and ask for either a compensation (some $$) or you contact ebay directly and tell them about the unjust treatment. Lawyers are expensive, but if you are determined to get the car for 64-65k, another thousand dollars in lawyer fees might pay off.
From a legal point of view, you have all the rights in the world to claim your M3, unless you reach an agreement with the dealer outside of eBay. Best of luck, and keep us updated.
(Jerez Black M3, 19", Extended Black Leather, Premium Pkg, Cold W. Pkg, Tech. Pkg, PDC, IPod, HD Radio).