If running an Ubuntu guest VM on Windows 8 Hyper-V you have a problem if you want to make use of a wireless network on the host machine. DHCP does not seem to work.
Firstly you have to create a virtual switch in Hyper-V
and connect it to your wireless card
you can then connect a Network Adaptor on the Ubuntu guest VM to the new switch.
Now for most operating systems this is all you need to do. The guest VM would use DHCP to pickup an IP address and all is good. However on Ubuntu 12.04 (and other versions judging from other posts), if you are using a virtual switch connected to a wireless card, DHCP does not work. The problem appears to lie in the way Windows/Hyper-V does the bridging to the Wifi.
You have manually set the networking settings. You need to track down the correct network using the MAC address. Remember that as the system is having network problems you might need to enable the connection (with the slider top right of the dialog if using the UI) before you can set the options
Once this is all set you should have a working network.
Now some posts suggest that you can avoid this problem if you use a ‘legacy network adaptor’ when you create the VM in Hyper-V, but this did not work for me. In fact even manually setting the IP address did not help on the legacy adaptor.