[Steve Hollasch]

Same problem here. I seem to get farther down the list by disabling my
network first, then re-enabling the network in order to flush the outbox when
done.

Others on the web have postulated that this is correllated with Outlook
sending or receiving at the same time, which might explain why it runs longer
with no net. However, I have still seen it hang when the network is disabled,
so this is not a full workaround.