I've had exactly the same stutter which made LFS unplayable, this started when I installed TEST PATCH 30.
I noticed the hdd light would flash furiously when the stutter occured, so I thought it was a prob with my hdd. Eventually I found that it was a rogue process that was running all the time... The process is called NMBigMonitor and it comes from the Nero Home 7 premium application. Ending task on the process would stop the stuttering every time without fail. I've since removed Nero completely from my system and I no longer have any problem.
I'm guessing there's something in the new sound system that has a tendency to conflict with other processes, as I doubt everyone else experiencing these problems are using Nero Home 7.
My specs are:
Asus A8V-E Deluxe motherboard
Athlon A64 3500+ socket 939 cpu
2gb Corsair DDR
Audigy 2 PCI
Powercolor radeon X850XT PCI-E 256mb gfx card
WD Caviar 320gb SATAII hard disk running in SATA1 mode.
Antec 480W NeoPower PSU
Running Windows XP, fully updated. Latest drivers for everything.
Now running Patch V, problem occured test patch 30 through to patch V.
Using Nod32 AV, problem persisted without it running.
using Windows Firewall, no connection issues.
Approx 13mbit ADSL2+ connection, model of router I can't recall off the top of my head. The router is configured so that my PC is on the DMZ, all ports handled through Windows Firewall.
Using AVG I found no spyware (fairly new install of windows, and the Nero process isn't considered malicious).
I recommend we all post our specs, both for Scawen and so we can see if there's common factor here.
ps: We just won the 5th test of the Ashes, that's 5-0 to Australia