Glitches when recording MIDI instruments - help!

[Id Lab]

One of the reasons I switched from Sonar to Traction was that Sonar was giving me glitchy audio when playing MIDI to a hardware synth and recording it as audio at the same time. The recording has obvious jumps in the waveform at regular intervals. Now Tracktion's started doing the same thing. Any advice?

I'm using a PC (Athlon 2000+, 512MB... good enough) with a Terratec EWX 24/96 card. It doesn't matter whether I use the EWX MIDI out or the one on my Edirol (USB) controller, it's still full of glitches. The sound's fine coming from the synth (a Korg EX-800 with the Moog Slayer mod, if anyone's interested). I've tried changing the buffer settings in three different places, with no success.

Any help appreciated.