Kernel_task eats CPU when MIDI system wakes up

Question

I have a MacBook Pro and a Focusrite Saffire (connected via firewire).
Noticed that the latest 10.5's are eating a ton of cpu when running Logic (or Ableton Live, my other DAW).
Digging around, using Activity Monitor I see:
when I plug in my Saffire, kernel_task jumps from 2% cpu to about 7%.
when I start Logic/Live, it jumps to 45-50% cpu and stays there (regardless of whether or not sound is being input or output).
Digging a little deeper, with no DAW running, I fire up Audio/MIDI Setup and switch the default output to the Saffire... kernel_task steady at 7%. Click on the MIDI Devices tab and kernel_task jumps up into the forties. Unplugging the Saffire, the cpu load goes down. Replugging, it does not go back up until I click "Rescan MIDI".
I have no MIDI devices connected to the Saffire (nor do I have any midi cables with which to try that experiment).
Using dtrace, I could probably dig more but I'm not on Apple's payroll and I'm too old to hack for free. I'd rather make music.
Fingers crossed that this can be fixed cause half a core is better used in a soft synth or something.

Answer 1

Seems like the problem persists when playing a 720p video on the external display set to 720p. To sum it up
Video Resolution
Main Display
External  (1280x720)
External (1920x1080)
480p
ok
fluctuating kernel_task cpu usage (~5 to ~150 cpu usage)
high kernel_task cpu usage
720p
ok
high kernel_task cpu usage
high kernel_task cpu usage
1080p
ok
high kernel_task cpu usage
high kernel_task cpu usage