An help to find hard lock cause

[Pierpaolo Follia]

Hi guys. I need an help to find why my laptop (a Sony Vaio PCG-K195HP,
Intel P4 2.8Ghz) is hard locking at least once per day.
I can't find any information in logs...or maybe I don't know how to read them.
My laptop simply freeze: I can't move mouse and keyboard doesn't respond too.
I tryed to disable powernowd ('cause I heard that was causing hard
locks for someone) but nothing.
I also tryed to disable DRI for my video card (ATI Radeon IGP345M). Nothing.
I tryed with vesa driver...and the system crashed after 2 minutes of usage!

Could anyone of you help me finding a way to resolve this problem?
Where have I to look?

I am Ubuntu addicted....I can't go back to Windows, and I don't think
that changing linux distro will resolve my problem.

Thank you very much

-- 
Pierpaolo Follia
http://madchicken.altervista.org/tech