Oracle released VirtualBox 3.2.6, a maintenance release of VirtualBox 3.2 which improves stability and fixes regressions.
If you want to see all the fixes and changes from here
Install Virtualbox 3.2.6 in Ubuntu
Download .deb packages from here once you have .deb package install by double clicking on it or using the following command from your terminal
sudo dpkg -i virtualbox-3.2_3.2.6-63112~Ubuntu~lucid_i386.deb
Or you can install using virtualbox repositories.