I ran into an odd situation today when I installed Virtualbox on a fresh install of LL2.2. I installed virtualbox from the "Install Additional Software" in the system menu. When I finish installing it says virtualbox can be found in the menu under system. I look and it is not there, so I open Install/Remove Software and type virtualbox in the search box and find that it didn't install the gui. I install the gui "virtualbox-qt", close the package manager and start a backup copy of a virtual machine with win xp on it, and i get an error telling me it can't find the kernel module. After closing virtualbox I reopen the package manager and install "virtualbox-dkms", I was not sure this would fix the problem, but it seems to have worked. I was able to start up my virtual xp and haven't had any problems yet.
Hopefully this will help others with this problem.