I use a contingent order as a way of setting a sell stop for options positions I'm holding.  I set the trigger for the contingency based on the price of the underlying.  If then I select the option to sell at Market pricing I get this warning:
Due to potential extreme fluctuations in pricing between the Last price and the Bid and Ask prices at the open, we highly suggest you do not place a market order on options after-hours. If you are sure you want to proceed, you will be held entirely responsible for the cost of the Order when it is executed!
Can someone please explain to me the risk involved with this?  Because of this warning, I choose a limit price instead and use the options pricing calculator to come up with my price, based on the trigger price of the underlying.  If there are any other ways out there for settings stops on options that make more sense, I'd love to hear them.  I'm only at level 2 trading, so I can't use spreads, yet.