Your kernel headers for kernel 3.0.0-12-generic cannot be found at
sudo apt-get install dkms build-essential linux-headers-generic
Building dependency tree
Reading state information... Done
E: Unable to locate package linux-headers-3.0.0-26-generic
E: Couldn't find any package by regex 'linux-headers-3.0.0-26-generic'
It would be easier if you said what the host and guest is.
If you ran the command and failed to get a response then the repo does not have the headers that match your running kernel. Post the above information and lets see what you are working with.
Perryg wrote:Check your Ubuntu repo settings. They should have updated during the upgrade but there might be a possibility that they disabled it and did not turn it back on.
Then do a apt-get update, then run the command again.