latency with traktor pro and fast track pro soundcard

hey folks, using a vci-100 and a fast track pro and just starting using pro. set up is all as before, but now getting major clicks and drop out problems. latency is set at 2.5ms and i can't understand why having problems as with this video card shouldnt have any issues, but there is a visible and audible lag when throwing the crossfader all the way across the cut between tracks, and there is a lot of clipping going on. running of a dell core 2 t7200, 3gb memory and with soundcard and vci as described. can anyon help???