Rejected Stop Order

[toptrader]

I've written a strategy that looks fine in backtesting, however in live trading the other day I had a stop order rejected. The message said invalid price of 616.6 (trading TF futures). The price looks valid to me, so the only thing I can think of is that the market was already below my stop price (I was long and the market quickly plummeted). However, I have a check in my code that should prevent this. Any idea why this would happen?

if (Close[0]>stopprice)
	ExitLongStop(stopprice,"LS","LE");
else
	ExitLong();

[NinjaTrader_Bertrand]

toptrader, you should check this off against the current bid / ask to avoid running into this issue.