A further update on the duplicate snipes...
This evening I created a snipe for an item using the "Snipe It Now" feature, closed all the AS windows except the NEW "My Snipes" window, and continued browsing ebay. I didn't create any more snipes. As I was just ready to quit, I clicked to the AS window, which showed the single snipe I had added. I refreshed the window, which required a data repost. Upon refreshing, the snipe had been duplicated.
I think at least sometimes, reposting data to the AS window that appears after the snipe was successfully added re-creates the same snipe in the list.