Xubuntu Restarts Automatically after Shutdown

I recently installed Xubuntu 14.04 on a Dell Workstation.

Whenever I shutdown, two things happen. Either it shuts down and automatically restarts, or it hangs at shutdown with a black screen.

Searching for a solution I have tried the following:

• used

  sudo shutdown -h now
  sudo shutdown -P now
  sudo init 0
  

• amended and updated

  /etc/default/grub to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force"

• checked the BIOS for Wake on LAN

  not an option for the DELL Precicion 7400 Workstation)

• reinstalled Xubuntu

None of these have solved the problems so far.

Anyone have any other options for me to try?

I recall having similar issues many years ago that was strangely due to the video drivers. If you remove quiet splash from your /etc/default/grub and run sudo update-grub, you should be able to find the specific place where the shutdown is getting hung up.