Hyper-V Program Manager
I do not know when this happened - but in the last couple of releases of SuSE Linux they have taken a weird dependency on the MAC address of the network card. To be precise - once you have configured your network card under SuSE - changing it's MAC address will cause SuSE to not initialize that network card (unless you remove and reconfigure it through YAST).
This is quite painful because - as I outlined here - Virtual PC can and will change the MAC address of the virtual network card from time to time. And in my case (as I regularly move my virtual machines between Virtual PC and Virtual Server on different physical computers) the MAC address is getting changed almost constantly.
Thankfully there is a relatively easy (though not intuitive) way to solve this. What you need to do is to get to a command prompt and type in the following commands:
Once you have done this you should be able to reboot the virtual machine and have the networking continue to work no matter what the MAC address is of the virtual network card.