Outlook 2007 SP1 / Vista SP1 - Can't Exit Outlook

Setting up new workstations. Office 2007 Basic and Vista RTM pre-installed by
Dell.

Joined to Small Business Server 2003 domain with fully updated Exchange
Server on a LAN. All operations appear to work perfectly. Outlook was tried
on network admin account, it auto-configured, works perfectly --starts-up,
shuts down on command. On two different non-privileged user accounts, Outlook
won't shut down after the initial setup.

NOTA BENE - using end task from Task Manager DOES NOT WORK -- it simply
restarts Outlook.

Trying to log off or restart workstation on these troubled installations
results in Vista error message reporting that Outlook is stalled, preventing
operation. Vista lets you log off/restart by terminatiing Outlook. I tried
adding the users to the Administrator group on the local machine, and retried
Outlook, with no better luck. Restarted machine. Outlook still hangs. Then I
removed the Outlook profiles, and re configured Outlook (automatic settings)
and it still didn't work.

At this point there are three differences between the scenarios that stick
out:

1) The first account (for Administrator) that works was the first one on the
machine.

2) The Administrator account has little to no mail in it. Tyhere are
moderate amount of filtered email in the other accounts, 20M in one 200M in
the other. However the accounts that don't work on the Vista - Outlook 2007
machine definitely work on the Outlook 2003 - Windows XP SP2 boxes in the
office.

3) The first Outlook installation was BEFORE Vista SP1. Vista "chews at" the
updates rather than letting you efficiently install them all at once like
Windows XP.

Any ideas?