If you have the same problem in ubuntu 12.04 the above solution might not work (at least it didn't work for me and another two - see the error I was getting in note#1 bellow). Installing the Oracle version of Virtualbox however worked just fine.
Note #1: I was getting the errors below:
ndemou ~ dkms status
virtualbox, 4.1.12: added
ndemou ~ sudo dkms install virtualbox/4.1.12
Kernel preparation unnecessary for this kernel. Skipping...
Building module:
cleaning build area....
make KERNELRELEASE=3.5.0-28-generic -C /lib/modules/3.5.0-28-generic/build M=/var/lib/dkms/virtualbox/4.1.12/build.....(bad exit status: 2)
Error! Bad return status for module build on kernel: 3.5.0-28-generic (i686)
Consult /var/lib/dkms/virtualbox/4.1.12/build/make.log for more information.