If you get this error when installing VirtualBox 4.1
sudo dpkg -i virtualbox-4.1_4.1.4-74291~Ubuntu~maverick_amd64.deb
dpkg: regarding virtualbox-4.1_4.1.4-74291~Ubuntu~maverick_amd64.deb containing virtualbox-4.1:
virtualbox-4.1 conflicts with virtualbox
 virtualbox-4.0 provides virtualbox and is present and installed.
dpkg: error processing virtualbox-4.1_4.1.4-74291~Ubuntu~maverick_amd64.deb (--install):
conflicting packages - not installing virtualbox-4.1
Errors were encountered while processing:
virtualbox-4.1_4.1.4-74291~Ubuntu~maverick_amd64.deb
Then simply uninstall 4.0 and install 4.1 as follows:
sudo dpkg -r virtualbox-4.0
sudo dpkg -i virtualbox-4.1_4.1.4-74291~Ubuntu~maverick_amd64.deb
You will also need to install the new VM extension pack from
http://www.oracle.com/technetwork/server-storage/virtualbox/downloads/index.html#extpack