incorrect processor speed detection

[dee <deetee@diversity-radio.net>]

I am running debian kernel 2.4.25 (in the form of demudi:
2.4.25-1-multimedia-686) on a toshiba portege 7140CT

I am having a strange and very impeding issue whihc is that on boot the
processor is sometimes misdiagnosed at a slower speed. I first noticed
this becasue when this happens my machine really does run slower!

So right now:
Detected 258.834 MHz processor.
(ooef!)

and previously
Detected 497.570 MHz processor.
(which would be about right)

also I've had a 381MHz detection.

I've googled a bit, and have concluded that whilst it could be the bios
settings relating to battery power-saving modes it is not actually this
because
i) the BIOS battery setting is set to proceesor speed=high
ii) this problem doesn't seem to be related to being disconnected from
AC power. Right now at 259MHz for example, I'm on the mains (& was at
boot)

This is slightly kookie, resolution only by random reboots, apparently.
Does anyone have any ideas?
thanks
dee