I had the same problem initially, seem to have fixed it now though.
All I did was set my virtual memory back to windows control, and freed up an extra 100 odd meg of space on C:
Havent had the lockup prob since, so im guessing it's a memory allocation thing.
Allso...your addons folder.....is there much in it? I read somewhere that every .pbo in that folder requires 'memory' when the game is started, so the more addons you have, the more system intense the prog becomes.
What I did, was simply create another folder, not in OFP for all my addons, except the BIS ones......when I want 'em for something, I move the .pbo back. This allso seems to have helped a great deal.
however, all this is just me stumbling around in the dark, i dont really understand these damn computer thingies very well

Hope this is of some help anyway.
Blue
PS. I'm running it on a Celeron 733 with a herculies prophet II MX and 256mg RAM, so, your system should handle it no worries.