Intel 10Gb on VMware (AMD) ESX 4.0 intermittent problem

Has anyone experience problems using Intel 10 Gb NIC on VMware (AMD) ESX 4.0? Some VM's are experiencing intermittent network drop issues even though the actual VM is online. The VM are unable to ping out or respond to ping and sometime unable to ping VM-to-Vm on the same physical server. The problem is only on some VM's on the same ESX host. We move the vms to another ESX 4.0 with same Intel 10 GB card, the problem is resolve, but return days later with same VM at new location. The Intel 10 GB has VMDQ features was not sure if that is part of the problem. Thanks in advance --Louis