Right this may seem a little farfetched but do you have a usb keyboard/mouse?
On my wireless desktop before i enabled "USB keyboard/mouse support" in the bios the mouse and keyboard would freeze every 10-20 seconds for about half a second then carry on as normal. I initially thought it was due to having too many usb devices (usb modem, usb wireless adapter, printer + kb/mouse) but it was just this option in the bios i had to change.
Worth a try if you have a usb kb/mouse.
80gb + 250gb WD HDDs
X-FI Xtreme Music