Always after update the kernel of my Fedora 10 x64, VirtualBox stop working. The problem I found was that VirtualBox requires a module to be compile for the new kernel.
To avoid all of the work to build the new module, I found a fast and effective solution:
After update to the new kernel, boot from it, open the shell the type:
# /etc/init.d/vboxdrv setup
This command will build a fresh new module for the current kernel.