MacOS – iTunes causes the entire system to crash when downloading some media OS X

I've had this problem for many versions of OS X and iTunes, though I'm currently running OS X 10.6.5 and iTunes 10.1 (54).

Sometimes, when downloading lots of Podcasts or iTunes U media, particularly when multiple downloads are enabled, I get:

1. The spinning beach ball over the iTunes window, but if iTunes is playing a video or music, it continues to play.
2. Other apps (like VLC) continue to run.
3. But I am unable to interact with the system or with any running apps and have to force restart with the power button.

However

1. No application is able send traffic over the network (Adium fails to receive new messages, pages in Firefox stop downloading).
2. I can't start any new apps, like the Terminal to look at what's going on — they pulse in the dock for some amount of time and then simply fail to start.
3. I can't invoke the force quit dialogue (nothing happens).
4. The mouse remains responsive, though after a time, I'm unable to focus on new windows.
5. Apple Menu > Restart/Shut Down/Logout do nothing.
6. The sleep button doesn't put the computer to sleep (it does nothing). Holding it shuts the machine down, which is my only recourse.

So, any ideas? I repair permissions daily (cron task), repaired the disk from the Snow Leopard DVD, checked out DiskWarrior, all to no avail.

An AKB article suggested moving my iTunes Library to an external volume, but I'm not interested in doing that.

What would be causing iTunes to crash my entire system? There doesn't, sadly, seem to be any helpful output from syslogd that correlates to the time of the crash. Could it be a corrupted iTunes Music Library?

EDIT — ADDITIONAL NOTES:
I have discovered a line in system.log that I thought was inserted right after I booted, but it looks like it might be crash related

iTunes[239]: INSERT-HANG-DETECTED: Tx time:5.596774, # of Inserts: 157, # of bytes written: 931894, Did shrink: NO

EDIT — FURTHER NOTES:
I have attempted to reproduce the crash with SpinControl running. Interestingly, I've seen iTunesHelper hang for the maximum sampling time, as well as iTunes, but not Finder. Even more interestingly (and infuriatingly) SpinControl crashes when I attempt to open logs flagged as "Very Unpleasant" or "App never recovered".

Following from some more research into people with vaguely similar problems, I have:

1. Rebuilt the iTunes Library (by trashing iTunesLibrary.xml and letting iTunes rebuild one); and
2. Re-installed the Mac OS X 10.6.5 Updater (Combo) as well as iTunes and repaired permissions.

We'll see if either of those fix the problem.

EDIT – AFTER CLEAN OS X INSTALL

I was so fed up with the problem persisting and bringing my system down, being unable to track down the problem (which could be anything from some random kext required by one of my numerous attached hardware devices to simply poor error handling).

Continued in a new question: iTunes OS X full system crash cont'd: is a bad media file the culprit? How do I isolate it?

THE ANSWER — NO SOLUTION

It seems that this is a (hardware?) bug with the Intel iMacs and Mac Minis, as I discovered in this thread on Apple Support (which admittedly wasn't easy to find with that title, but it fits my problem to a tee).