A new version of VirtualBox is out. The webpage says it is the most signifigant upgrade so far. The forum seems to indicate that it is best to uninstall the old version and then install the new one.

After the uninstall/install everything will be the same as before (all users who were a member of vboxusers will still be, VMs will still be there, etc.) No problems at all for me.

I downloaded the package for my distribution (Debian Etch) from the website and used the following commands to perform the operation.

dpkg -r virtualbox
dpkg -i /share/apps/virtualbox_1.4.0-21864_Debian_etch_i386.deb

Now you're ready to run VirtualBox just the same as before and enjoy the new features.