Now there's a point. Possibly not. Do the games crash the instant they finish loading? It could be that your Power supply isn't stable enough. A 600W unit is plenty to run most crossfire setups. However, a lot of "600W" units are nowhere near as high as they claim to be. What is the brand of the power supply?
The P45 Platinum requires a molex power connector plugged into the board to power the second slot. Have you attached this power connector? it is just above the dark blue PCI express slot.
Which OS are you using? It is also possible that the second slot on your motherboard is faulty, or that the second card you've bought is faulty. Try a single card in the bottom slot, and try switching the two cards round.
No, Sapphire cards had a glitch a long time ago with firmware that could cause them to crash when a game loaded. However, this was meant to have been fixed many months back, and I've yet to hear of a single case of it since.