Posting this so others may find this solution.

Recently, my box was hanging.  I noticed in my dmesg
"k8pnow_read_pending_wait: change pending stuck."

Essentially, when reducing the vid and fid (Cool'nQuiet,) something
goes awry.

I had recently replaced my video card with something else, then
something else again.  Both these cards were causing the problem.
The culprits are a radeon 9000 all-in-wonder and the integrated via 
unichrome pro igp video on the K8M800.

Googling for the problem, I found cases of linux users with the
same problem.  Some indications are that the EVGA e-GeForce MX 4000
will also cause the problem.

It seems that this is a problem with the K8M800 from via.  Here's
the link to their product page:
http://www.via.com.tw/en/products/chipsets/k8-series/k8m800/

The A00 revision of the Matrox G45+ (G450) works fine though, that's
what I'm currently using.

So: avoid the K8M800 unless you have a cache of video cards and you
don't mind which one you use.  Hell, I'd just avoid the K8M800, the
damn integrated video on the chip does not play well with the rest
of the chip!  Seriously, guys.

-- 
Travers Buda