I had the same problem, several snipes set to go, and none were placed.
Fortunately for me, in a couple of them I had placed proxy bids (kind of low), and no one else bid so I still won. (Just lucky I guess)
But the others that were won by lower bids kind of burned me. Now I don't trust AS to place my bids, I watch and "snipe" it myself (bid last minute) when I really WANT the item.
It bothers me that I don't trust AS to perform anymore, it's so much more trouble to do it yourself.
Tired and shagged out after a long squawk....