I guess uninstalling everything but the kitchen sink must have helped.
Seriously, I think uninstalling Google desktop did the trick. Never before
was I able to run IE7 x64 for more than a few minutes without it crashing.
I've now been running it over about 15 minutes, using multiple tabs, and
otherwise abusing it. No crash.
The funny part is that Outlook 2007 seems faster as well! Now if MS would
just come out with an x64 version of WDS I would be set.