with the recent upgrade I got a problem with virtualbox that has something to do with permissions on /dev/vbox* drivers. the error I can see from virtualbox logs is like the following 'Failed to open "/dev/vboxdrvu", errno=13, rc=VERR_VM_DRIVER_NOT_ACCESSIBLE'.

a quick search tells that the permissions on following drivers is wrong, but I cannot figure out the root of the problem.

1. ls -l /dev/vbox*
   crw------- 1 root root 10, 55 Nov 30 15:41 /dev/vboxdrv
   crw------- 1 root root 10, 54 Nov 30 15:41 /dev/vboxdrvu
   crw------- 1 root root 10, 53 Nov 30 15:41 /dev/vboxnetctl