Does Steam have an FAQ or forum you can check?
Did you try emailing Steam's support, or supportintl@dtp-entertainment.com / support@larian.com?
There is another patch being released this 'summer' (no official release date, but expected around the release of the add-on), which could conceivably help.
Do you have any other games that use PhysX, or is there a demo / benchmark you could try to see if the problem is PhysX itself, or with D2:ED starting PhysX?
