ACPI related process hangs on T42p

[Johannes Hofmann <Johannes.Hofmann@xxxxxx>]

Hello,

on my Thinkpad T42p processes start to hang after the system has been
running for a while, when ACPI is enabled.
Then one process after another hangs, but the system remains responsive (at
least for a while) and I can switch to the kernel debugger.
So far all process were hanging in state biord and could not be killed
anymore.
Any ideas, how to track this down?

Thanks,
Johannes

PS: Apart from that problem, ACPI seems to work fine. I can even throttle the
    CPU down.