Computer started to reboot instead of shutdown after kernel update

Not sure if this is a bug, though it appears so. I followed the suggestions in the guidelines to ask a question if I am not sure. I'll try to give a technical account of what is happening but I am not familiar with developing software.

I am running Ubuntu 12.04 64bit with Gnome 3 on a dual boot machine. Upon shutdown (from the menu) the computer stops, including all the fans but starts by itself after about 2 seconds.

This started happening after an update that changed the kernel from 3.8.0-33 to 3.8.0-34. I can choose a previous kernel from the GRUB menu at startup and boot with 3.8.0-33 and this way I can shutdown the computer. I can also shutdown the computer with no problem when I boot into Windows. Today there was another kernel update, which I did and can report that the unwanted behavior continues also with 3.8.0-35.

Things I've done:

- Checked the BIOS for settings that might prevent computer from powering off. No "wake on LAN" or other settings like this are active. The mainboard is based on an Intel H87 chipset.

- Added "acpi=noirq" to GRUB - no effect. If it brings any relevance: I recently upgraded my video card and the issue persists with the new card.