can't restart / shutdown sometimes in VirtualBox.

Official 47961.
Sometimes when you want to restart you can't, nothing happens.
The debug log shows:
WARNING: MmUnlockPageableImageSection at ARM³::DRVMGMT:39 is UNIMPLEMENTED!

If you try to do "shutdown -r" you get:
ERROR_ACCESS_DENIED - Access is denied
Error code: 5

This started after http://svn.reactos.org/viewcvs/reactos?view=rev&revision=47934

Haven't found a replication method yet. Problem has been experienced also by niski. Filing like this atm so we can keep track of it.