You could try getting rid of most of the auctions and just using fixed price/immediate payment required. I see a couple of things on just a quick look that might do better on auction, but most you can probably put a pretty good ballpark price on it. That way you don't have to deal with bogus bidding and the like.
It's a shame, though, that this is happening, but you're not alone.
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Against stupidity, the very gods themselves contend in vain. -- Friedrich Schiller
Hell is empty. And all the devils are here.
