When you powered on the copied VM's for the first time you should have received a question about whether the VM was copied or moved!? How did you answer this question? In case you selected "I copied it", ESXi generated new UUID's and MAC addresses for the VMs and you have to reconfigure the network within the guest OS. Can you confirm you did this and/or the IP settings are still how they should be? Are there any warnings/errors in the Windows event logs?
André