Reply to 2.6 and Distortion

So I moved straight from 2.1.2 to 2.6 and I have this one really annoying issue lingering.

After playing for a while I get some nasty distortion which comes from all my channels. It starts faintly but then after 30 seconds or so it gets really bad. Nothing other then a restart of my comp can fix this.

Im using TSP with an external mixer, with a core 2 duo mac with 8GB ram.

Anyone experience this or have any info to offer?