I agree that a prudent owner would check owner B's other bids and see that there is a mistake. However, we all know stuff happens and mistakes are made. We should have a rule set up ahead of time in the event this happens.
For my two cents, staying with grayfoxx's original example, I'd say the clock should still be reset to the time of owner B's bid. Too many other people may have acted believing the bid was true. Tough luck for owner A, but at most it costs him a day and he could still win the bid at the original price. Hypothetical owner C was going to outbid him anyway, everything just slips back a day.
Also, there should be some form of punishment for owner B. Dock him $10 million maybe?