I've seen that happen before. An IT colleague of mine at work said that it looked like a glitch on the bidders PC....he said "to put it simply" (for me?) the users PC normally sends the bid, which Ebay's computers record and acknowledge by sending a response, and that's that. If the users PC has a corrupt file, it may fail to receive the response, and get into a loop which keeps sending the same bid again and again. He said it was unusual, as programs and apps have a fail-safe to stop this.