ubuntu 14.04 freeze on restart and shutdown

[Photorelease]

Hi all,
i cant restart or shutdown the computer.
already tried

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash reboot=bios"
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash apm=power_off"
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash reboot=pci"
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force"
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=off"
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force apm=power_off"

even in the terminal, doesnt work
$ sudo shutdown -h now

and always get this message:

*killing all remaining processes... [fail]
*deactivating swap... [ok]
mount: / is busy
*will now halt

i'm using one dell precision m90.

any idea? thanks all

[christo3]

Save yourself the trouble and backup your data and .deb packages and do a complete reinstall. if you're not a novice ( like myself) and wan't to learn fixing broken systems , go ahead .

[Photorelease]

yep... but i already did a complete reinstall and the problem keeps the same...

[dragonfly41]

From a simple google search .. try this .. http://ocaoimh.ie/2008/02/13/how-to-...evice-is-busy/

substitute your ubuntu 14.04 partition .. /dev/sdax .. in commands