After first time i hit this issue, I did a clean install of 4.3.14RC1 and I still have this error, can't start any VMs.
Screenshots:
VM logging does not even start, so there is no VM log, and this is what I can see in VboxSVC.log:
00:29:09.277842 ERROR [COM]: aRC=VBOX_E_INVALID_VM_STATE (0x80bb0002) aIID={480cf695-2d8d-4256-9c7c-cce4184fa048} aComponent={Machine} aText={Machine is not locked for session (session state: Unlocked)}, preserve=false
00:33:43.393153 Watcher ERROR [COM]: aRC=E_FAIL (0x80004005) aIID={480cf695-2d8d-4256-9c7c-cce4184fa048} aComponent={Machine} aText={The virtual machine 'centos1' has terminated unexpectedly during startup with exit code 1}, preserve=false