well here's something that points to drivers, i have had 3 different 4850's
single mode and xfire and they all artifacted in crysis, stock or oc'd 1 card or 2 but they had no stability problems. In the scene when the sun comes up in the beginning of the game, when i crouched near the rocks and the shadows and were being rendered on the rocks i got white sparkly's on the rocks. Then i ran down into the shed/house/hut whatever on the shore and the wood and walls inside did the same thing. I hate crysis anyway its just a bench to me.
this points towards an ati problem or driver problem in crysis.