The same problem occurred in my game, and I my computer has 1Gb of RAM.
At that time, updating the nvidia drivers seemingly solved the problem, but I should warn you that newer drivers can cause problems.
Others (and myself
) have been reporting that the newer drivers cause system instability and game crashes too, and the only way to get rid of them is to downgrade the nvidia drivers to an earlier version.
By the way, after downgrading my drivers, I can still take pictures, maybe it's a problem that was fixed in OFB?