Vista - Hard drive light stuck on with Vista SP1

I've noticed a weird behavior with Vista SP1. I have a custom-built PC with a
Gigabyte motherboard (GA-P35-D3SL) that is running a ICH9 soutbridge. I'm
running it in ACHI mode. Before SP1, it works just fine. However, once I
install SP1 I've noticed that the hard drive activity light sticks on after I
resume it from sleep. If I boot it the first time, it'll work normally, but
after I sleep/resume then it sticks on, even if there is no disk activity (as
shown by the performance monitor.) Uninstalling SP1 undoes the behavior, so
it's definitely being "caused" by SP1. I've installed/uninstalled SP1 several
times, and the behavior is consistent.

My guess isn't that there's disk IO but rather something changed in the
sleep/resume that is now causing issues. Along with this I've noticed that my
CD spins up a bit later when coming back from a sleep which is fine but hints
that something changed in this part of Vista. I normally wouldn't care too
much but I kinda want this to work: it's how I always check if any slowness
on my machine is due to disk latency or due to something else (and perhaps
with many years of ingrained habits assuming that such a light will work!)

Is there any guesses as to why this is happening? Is there any known
registry keys or something that I can use to revert just this part to the
"old" behavior without entirely uninstalling SP1?