I use to have virtualbox installed in my machine from the packages provided by virtualbox.org.A few week ago I replaced it with the OSE available from the Debian repositories. One package that wasn’t available for my architecture (amd64) was virtualbox-ose-modules. Installing virtualbox-ose went without problems but when I started a virtualbox I received a message like:

VirtualBox kernel driver not installed. The vboxdrv kernel module was either not loaded or
/dev/vboxdrv was not created for some reason. Please install the virtualbox-ose-modules package
for your kernel and execute '/etc/init.d/vboxdrv start' as root.
VBox status code: -1908 (VERR_VM_DRIVER_NOT_INSTALLED).

Asking Mr. Google “he” gave me the answer by pointing his artificial finger to: http://www.esdebian.org/forum/print.php?id=115990&forum=15 and to: http://debaday.debian.net/2007/12/05/virtualbox-a-virtual-pc-for-you/ So I did, as root:

# aptitude install virtualbox-ose-source module-assistant
# m-a prepare virtualbox
# m-a a-i virtualbox
# dpkg -i /usr/src/virtualbox-ose-modules-*
# modprobe vboxdrv

and after that virtualbox worked like a charm