no C States on Asus L3D with 2.6.22.9

Hello to the list.

I stumbled over erratic behavior with a 2.6.22-14 (Ubuntu) Kernel. The computer is an Asus L3D (L3000D) with an Athlon XP-M 2500+ processor. The content of /proc/acpi/processor/power reads:
--snip--
active state: C0
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
--snap--
This is reproducible with a vanilla 2.6.22.9 kernel.

Older kernelversions (e.g. 2.6.17) showed only the C1 state as available what is quite few, yet more than the current state.

I would be thankful for any hint what to do to investigate this further.

Thank you, and with best regards,

Jan Ries