I am also getting the same error:
I'm also not getting any sound. Even with all the volume controls set at maximum.
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, e.g. virtualbox-ose-modules-generic..
VBox status code: -1908 (VERR_VM_DRIVER_NOT_INSTALLED).
I'm using Kubuntu 8.04