In instant tournaments, "mechanical errors," such as someone with shaky hands clicking pass on the way to a bid, cannot be undone. (If it can, I am unaware of it.) I understand the problem of letting players rethink an action before changing it, but purely inadvertent errors? Just today, this auction arose: 1NT (me) - P - 2C - P - P!!! On the way to bidding 2S, I somehow clicked on the pass icon. End of story, withdraw from the tournament (iMPs, 2C in a 2-2 versus 4S, vul!), pay your money again, and start over! Surely there is some way to build into the software a short "undo" before the activation of a bidding choice? A single second would have been enough in a case like this.