The problem is the Insyde H20 BIOS on this laptop and there are some new Toshiba Satellite notebooks with this problem. I found here http://swinky-linuxblog.blogspot.com/20 ... -l305.html
a solution for my problem. So I put in /boot/grub/menu.lst comment:
title Ubuntu 9.04, kernel 2.6.28-11-generic
kernel /boot/vmlinuz-2.6.28-11-generic root=UUID=a91f.. ro quiet splash acpi_osi="Linux"
So, I'm not using anymore the omnibook module I tried before, the fan is working ok, my notebook doesn't restart by itself from now, remains only to solve the problem with Fn+Fx keys for brightness control.
Thank you for your time and support !