Set it to run in a 4:3 resolution, NOT stretched. Widescreen messes up registration if it's stretched. You can tell if it's stretched because everything will be 1.5x it's normal width.
In addition, check your FPS with Fraps or GC. If you get below 60, lower your res, or detail, or AA, etc. Turn off shadows, set detal to medium or low, etc.
CSS is nub compared to 1.6, but it does have a solid CAL league behind it among others if you play competitively.