@oibaf I've just installed the newest updates and now have kernel 3.2.0-56-generic-pae (12.04 32-bit), but the error message still appears. I haven't used this computer recently, so it is hard to tell if there is a problem with lock-ups. But, as I said before, after updating to 3.2.0-54 I didn't experience lockups, so probably this part of the problem is fixed.
@oibaf I've just installed the newest updates and now have kernel 3.2.0-56- generic- pae (12.04 32-bit), but the error message still appears. I haven't used this computer recently, so it is hard to tell if there is a problem with lock-ups. But, as I said before, after updating to 3.2.0-54 I didn't experience lockups, so probably this part of the problem is fixed.