Since I installed a new mainboard, which is a Biostar TA770 A2+ (V5.2) some months ago I experience the following strange behaviour on my machine, which is running Ubuntu 12.04: Everytime I try to shutdown or poweroff my computer it instantly reboots. It doesn't matter if I use the button the Unity desktop provides in the upper right corner or if I use some commands like
sudo shutdown -h now or
sudo poweroff. Everytime the computer switches off (even the fans do get silent for a split second, which does not happen if I hit the regular reboot button) and then the machine is rebooting again. The only way to shutdown the computer is to completely switch off the power after it has shut down.
Here's some additional information: The "standby"-mode works perfectly fine. And, if I send my computer into standby state, then wake the machine up again and then try to shutdown it using for example
sudo shutdown -h now it turns off completely without rebooting.
Anyway, I already tried the option
acpi=noirq in the grub config file, but without any success.
I would be very very grateful to anybody who could help me out with this one.