I have the same exact problem, same computer model. I believe it's ACPI related.
Linux 3.2.0-29-generic #46-Ubuntu SMP Fri Jul 27 17:03:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
Description: Ubuntu 12.04.1 LTS Release: 12.04
I have the same exact problem, same computer model.
I believe it's ACPI related.
Linux 3.2.0-29-generic #46-Ubuntu SMP Fri Jul 27 17:03:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
Description: Ubuntu 12.04.1 LTS
Release: 12.04