reboot instead of halt

Hi,

 I have a Gericom 1st Supersonic notebook. I am using it since 2.4.14 or
so. 2.6.8.1 runs fine, but 2.6.9-final and some older kernels I have
tried (2.6.9-rc4, -rc3, -rc2) all have the following problem:
when I type halt, the notebook shuts down, but restarts. I have read
that there were problems with APIC, but I have already switched off all
of that. What else should I look for?
If relevant, I use Debian Sarge, with my own compiled kernel, which has
the same config file the previous kernels had.

Thanks,
Laszlo/GCS