this worked for me and made the game playable again (25-30ish fps)after having all the same probs as everyone else....i`m running an e8400@3.6ghz 4870x2 4gb ram xp sp3....check your virtual ram/page file settings and if possible move it to another hard drive and see what windows thinks your system managed size should be(mine was 6gigs!)the more the better and set it to that,restart computer,then start the game with low to normal settings and crank them up until your fps start to drop,the artifacts stopped appearing and the game stopped crashing for me.
hope this helps.