Is your VMware host dropping packets but the host network seem fine?
Check to see that you don't have a network storm due to loopback or other device failing in the network - you never know when a user will bring in equipment that can make your bridged vm network get poisoned like the arp tables in the switches in the environment.
Also, if you have a backup copy of a VM, make sure it has a different MAC address before firing it up. - thanks other folks on the net for that thought, proved not to be my issue, but a good one to watch for.