I have a Win2k8 guest running on ESXi 4.1. The host has 12 cores and the problem happens even if the guest is the only VM on the host. We have 4 cores dedicated to the guest. We noticed that network starts chocking when the CPU load goes up. After some testing we noticed that when running a simple CPU hogging tool set up to run 3 threads at 100% the regular CPU load goes to 75% like it should and the "kernel times" graph in task manager goes up to 25%. My intuition tells me that the network problem and kernel times problem are the same. This is confirmed by another similar VM we created on the same host which doesn't have either of the problems. VMWare tools are obviously installed. The nic is e1000. What else can we do to troubleshoot this?