I have to agree .. its on your pc most likely
I had a bad mainboard that spikes its varience , but the host time says nice and low , i double checked by using a second pc .its varience was nice and flat .
Ive also seen bad varience's from virous's,p2p file share,message,auto up date, and other programs that run behind ah while playing.
Also the Virus guys are at it again real heavy and its congesting the net again .(last nights primetime usa was a mess)