I might be naïve, but from my point of view, if a file exists, it has a good reason to do so... Therefore, I like better to edit the file, and correct the rules rather then to remove it.

Stop networking and udev:

/etc/init.d/udev stop
/etc/init.d/networking stop

Then, edit the persistent-net.rules file:

On Ubuntu: /etc/udev/rules.d/70-persistent-net.rules
On Debian: /etc/udev/rules.d/z25-persistent-net.rules

You will find two instances. The first one is the one from the template virtual machine. The second one is the one attributed when answering "I copied it", on first start:

# PCI device 0x1022:0x2000 (vmxnet)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:36:xx:xx", ATTR{type}=="1", NAME="eth0"

# PCI device 0x1022:0x2000 (vmxnet)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:75:xx:xx", ATTR{type}=="1", NAME="eth1"

Delete the 1st one, and change eth1 to eth0 at the end on the second one. You will end up with:

# PCI device 0x1022:0x2000 (vmxnet)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:75:xx:xx", ATTR{type}=="1", NAME="eth0"

Save the file (obviously), and then restart udev and networking:

/etc/init.d/udev start
/etc/init.d/networking start

And it works. You don't need to reboot your machine or what so ever, and you don't have to delete that rule file.

thanks guys for posting the answers on this one. It was doing my head in when my vmware servers just lost their networking!! Not sure if the original cause was due to cloning as I did have it working after cloning for a considerable period, but no matter, the fix of removing this persistent net rules file and rebooting worked for me!

Excellent stuff guys.