actually it canßt be the vswitch anymore, as the fresh installed naked win2k8 is not loosing any packages .
We cant work around naked though 
I tried out the experiment with Win7 and a Win2k8 and the ping was proper. I was using R2. These were not running any load. But when I started iozone on Win2k8, I was able to see 1 or 2 packet drops for every 10 mins or so.
When you say naked Win2k8, do you mean without VMware tools also?? Also, I had asked for the drivers present in the Windows machines. vmxnet3 or e1000e?