question about kernel 2.6.1

Hi,
i have a sony PCG-FX505 laptop (ati graphic and 1,2 GHz mobile athlon).
I use fedora linux version 1.0. The system runs o.k.
After the installation of the kernel version 2.6.1 i can't shutdown the
system. The commands 'halt' and 'poweroff' doesn't switch off the
device.
The display is black, but the LEDs are still on.

Any suggestions where to start solving?

Best regards,
Roman Jordan