opened USDCAD closed with a price from AUDUSD????

 
I have a problem here. Testing a theoretical model as expert I let it just run. Now the account has balance -4333.
One trade has a loss -5509 because the price of USDCAD has moved from 1.1654 to 0.7514. It could be normal but there is no such price in the history. there is a chance that it readed something wrong or there was a bad tick.
It happened 13.01.2006 08:32 according to account history. I have build .186

How can I protect myself against those kind of things. Is there something I can do?

Why it did close all positions anyway, is there something like margin call? if there is at what level it works. I can remember that few weeks ago my code was few moments in negative territory without any problems whatsoever.