Has anyone noticed packet loss in Win7 or Vista that is not present in the same hardware running WinXP?

I have tested this on two separate computers on two separate internet connections (both were using Comcast residential connections). Both computers use the built in NIC on the motherboard (one realtek, one marvell) and are connected (via ethernet cable, not wireless) to the internet through D-link routers (two different models) and mototrola cable modems.

When using a free ping tester to ping a site like google.com at a ping frequency of 1 per sec, the two computers when running WinXP pro will have a packet loss percentage of about 0% to 0.2% if left to run for a couple of hours. On the same computers (dual boot- one with Vista ultimatex64 and the other with Win7 prox64), the packet loss is about 6 to 7% with Win 7 and Vista if left to run for a couple of hours. Seems like a significant drop rate... (all drivers are up to date- I double checked the LAN drivers several times to be certain).

I've seen a few similar posts scattered around on different sites but no universal culprit for the packet loss (other than vista/win 7).