My comp is an Pentium 4 3ghz with a gig of DDR ram and a Radeon 9800xt video card and I have the same or a very similar problem. It doesn't happen with NS, and it doesn't happen with TS, but it happens with ESF in both WON and on Steam. I start playing, I get good framerate for a while, things are ok for a couple of minutes, then the framerate starts to drop, I start getting jagged gameplay, then it gets a little worse, then a lot worse, then eventually it freezes completely. Sound like a memory leak?
I've tried reinstalling ESF in the past and it hasn't changed the problem. Back when I had an Nvidia card I had the same problem but it took much longer for the game to crash than it does with my Radeon 9800, and this is an entirely different PC. That was an AMD processor, this is a Pentium, that was SD ram this is DD ram, Nvidia and Radeon, Won and Steam. Obviously with a new PC there must be a new reason why it is crashing, so perhaps someone out there can give us some advice other than "you must be using software mode or have a crappy computer."