After resuming my VMs from a power failure the other day, I discovered that one of them won't be seen on the network any more, even though it THINKS it has a network connection. When I ping anything else, it says "hardware error". It cannot be ping'ed, and I think it's pretty much broken. The short of it is that you need to reinstall the VMware tools and "update driver" for the network card, and it's fixed.
VMware's link to resolving this (with instructions) is here.