I had a problem a couple years ago with windows freezing for a quarter of a second or so and happen rather often. I found that disabling my PCI network card cause this to stop, and bought another card, only to find that any cards in that slot caused the same problem (couldn't test other slots due to double-slot graphics), so I wrote it off as a bad PCI slot and bought a wireless bridge.
Earlier this year I upgraded to a z68 motherboard (along with cpu and ram). I didn't need wireless until recently (and now the bridge is gone), but a couple weeks after adding in one of the old PCI cards, I noticed the same problem. Every few days it will go into a period where these freezes occur every second or so and I have to restart (or disable the card in the control panel) to stop them. As you can probably guess, network connectivity is disestablished while this freezing/stuttering is occuring.
Any advice? Anyone have experience with problems like this? P.S. I did notice that windows applied an update on restart this last time. Maybe it's just coincidence.