This is a Microsoft known issue described in the following KB article:http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1020078
"During template deployment or cloning, new virtual hardware is created for the destination virtual machine. Network interfaces are assigned new MAC addresses. PCI Express devices, including the VMXNET3 virtual ethernet adapter, a new serial number is generated as well.
Windows 2008 R2 and Windows 7 track PCI devices by which slot the device is connected to. Moving a PCI network interface between slots will allocate a new set of settings for the NIC as it is considered a new device. Replacing a PCI network interface with the same make and model will retain use of the previous settings. However, PCI Express devices are tracked by their serial number, which is derived from the MAC address.
When a virtual machine is created by cloning or template deployment, the new virtual machine's PCI Express virtual network interfaces have different MAC addresses and serial numbers, and are detected as new devices.
The same behavior can be observed by deploying clones of Windows 2008 R2 or Windows 7 on new physical hardware with PCI Express network interfaces in the same slots."