If you the installed VirtualBox from a .deb file downloaded from www.virtualbox.org instead of installing using the apt repositories then it might have left some badly formatted version numbers in /var/lib/dpkg/status and /var/lib/dpkg/available which break when you try to use dpkg in Maverick after an upgrade.
The solution is to search and remove all instances of "_Ubuntu_jaunty" from lines beginning with "Version" in those files.