hey cobra,
to say that single player is fine and not mp, doesnt mean your drivers are not causing probs.
when i first started online gaming and was an even more of a noob, mine was the same.
single player settings as hi as i could, then when i played online with TTF at splinter cell, part way through game it would crash.
TTF updated all my drivers and then it ran sweet.
give it a try, at least then you can cross it off the list of a poss prob.