kern.hz=1000 causes random poweroff on laptop

Hi,
I have a laptop sony z505rx, that if booted with kern.hz as 1000, will 
power off within a minute or two of booting. It does this regardless if 
you boot with or without acpi. It is rock steady with kern.hz at 100.

On this particular laptop, most of the peripherals are routed through 
irq 9, including acpi (ie cardbus, fxp, etc), so it might be that 
running with kern.hz at a 1000, tickles an interrupt storm, but it is 
hard to debug as the machine just goes completely dead.  The hard drive 
is powered off (at least that is what is sounds like), the screen goes 
black, and no interrupts are handled.

Any ideas as to what the cause might be? Anything I can do to pinpoint 
anything?

Thanks,

Lars