I've had this happen a couple of times even though I will wait a long time before relisting. My partner occsasionally gets a bit anxious......
Your options are limited....but here's a few
Contact the current high bidder and honestly explain the situation, whether to do this before or after is hard to say.
Don't say anything but later claim the item is non-functional or not as described. "I was just testing it before I sent it out and it went up in smoke" or "I never noticed but there's a giant crack in the screen"
You run the risk of a neg in either case, it all depends on the buyer and your communication skills (or how nicely you lie). You could just refund the first buyers payment but you lose the extra money and may still get a neg. Although the original buyer didn't communicate, he did pay and from the sounds of it approx. 2 weeks after the auction ended, this is slow payment but certainly not outrageous.
Relisting after only a week to my mind is too fast even with no contact. Unfortunately it's put you in a position where one of your buyers may not be happy. A neg from buyer 2 will at least be balanced by the extra cash, a neg from buyer 1 means both a neg and less money.
What to do what to do..........
Ben

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915
- answering Trolls is voluntary, my policy is not to participate.