It's me again.
I see noone has an answer for this problem.
I did some tests on the server and tested the old kernel versions.
In my /boot/grub.menu.lst i was having:
I have modified that to:
And now i can choose from a list wich kernel to boot.
I have tested all 3 versions i have ( 184.108.40.206-99.fc12.i686, 220.127.116.11-70.fc12.i686 and 18.104.22.168-174.2.19.fc12.i686 )
After booting each one i have run a mpstat -P ALL and with all 3 kernels i was having a result with only one CPU instead of two.
I still don't want to think that this could be a hardware problem but... you can newer know.
So.. i yell at you all, if is someone who had or has this problem please let a message here. Maybe we find an answer for this problem.
Than you all in advance