Repeated crashes, in game. Cause?

[Subjective Effe]

I'm getting a weird crashing issue in-game and it's not in the "known problems" list.

Specs.
CoH: Opposing Fronts, steam version obviously.
Computer specifications ;
Graphics card is a G force 580 series, and I've never had any problems with it as regards game performance.
CPU Intel core 2 duo, quad core.
4 gigabytes RAM.

Often whilst playing a game the game freezes and crashes. I find this happens most often when a game has been going for at least 15 minutes.

The game is up to date and I don't have any crashes of this type with any other programs. Apart from this problem the game runs fine.

Does anyone have any idea why this is happening or how I can stop it? It's starting to affect my ranking because I lose games when my computer crashes even if I'm actually winning them.

So frustrating!!