Thanks for all the advice.
I did manage to track the problem down to my soundcard based on the aureal vortex chipset. I have just swapped mine and my flatmates soundcards over this has solved the problem.
For any intrested here is an explanation of the problem:
"The following problem was noted for VIA KX133 chipset motherboards before the KT133 chipset was released. The KT7 motherboard uses the VIA KT133 chipset which is very similar to the KX133 chipset. The following comments therefore apply to the KT7 and KT7-RAID motherboards.
For audio cards that use A3D audio chip there appears to be an incompatibility that causes the KX133 system to deadlock when system traffic is heavy. The reason for this is that the A3D chip issues one memory read request cycle to the North Bridge and expects a grant within 4 mico-sec of latency time. If PCI TRDY# is not asserted after 4 mico-sec, the A3D hardware will de-assert the FRAME# and REQ# to terminate the operation. However, the A3D audio software driver cannot acknowledge the termination and continues waiting for hardware response. Hence the system hangs. This issue will only occur during heavy system traffic when the North Bridge cannot grant access to A3D audio chip within the 4 mico-sec latency time. There is no known work-around for this issue, and the principal advice is not to use A3D-based sound cards with KX133 based motherboards. Source: VIA Application note Serial #AN137 Date 07/05/00. This information found at BrokenPixel "
from
http://www.viahardware.com
