Another thing to try is to dig around in your motherboard's BIOS, since most motherboards nowadays have Linux listed as one of the choices under "Installed OS". Also check the motherboard manufacturer's website to see if there is a BIOS upgrade available for your motherboard.
Please let me know if this fixes the issue and good luck!
This is not a definite fix, but rather a workaround. Try disabling ACPI altogether. There's a nice forum thread on the topic: http:// ubuntuforums. org/showthread. php?t=2620
Another thing to try is to dig around in your motherboard's BIOS, since most motherboards nowadays have Linux listed as one of the choices under "Installed OS". Also check the motherboard manufacturer's website to see if there is a BIOS upgrade available for your motherboard.
Please let me know if this fixes the issue and good luck!