My Asus L4500R notebook

Hi all, I have problem while booting my Asus L4500R notebook. I have both Knoppix and Win XP installed.
The problem is : at bootmanager's screen when I choose Linux (2.4.* or 2.6.* kernel), it writes out :
Loading Linux ........................
Bios Data Check successful
and it hangs.

BUT : this ONLY happens when I boot Knoppix FIRST when I turn on my notebook.
It's weird that : IF I boot WinXP first, then RESTART (not SHUTDOWN), I can boot up Knoppix.

Anybody knows what problem it is ? , does WinXP write something to BIOS(that Knoppix cannot) so Knoppix can use it to load other hardwares ?

Thank you.

When I give the option: acpi=off then it boots to Knoppix, but the new problem is that I cant shutdown with shutdown -h now , I have to push the Power button after it halts.