I recently installed 12.04 on an HP Spectre XT ultrabook. I installed 12.04 from a USB. When the install was complete, and the computer restarted, I got a blank screen.

After some searching, I found that I had to choose "acpi=off" during the installation, which now shows up in the grub screen.

Once I was on 12.04, I upgraded to 12.10.

The issue now is that when I hit shutdown, the computer hangs on a purple shutdown screen. Usually, at this point, I press the power button on the machine to completely power off the machine.

I am new to ubuntu, and would appreciate the help. Thanks.