Arthur wrote:

1) The Outlook Data File is open and I can access messages in there
labeit with excessively slow performance (about 10 times slower than
with WinXP/Outlook 2003).

2) I CLOSE the file from inside Outlook.

3) I attempt to eject the USB Flash Drive: Vista says NO, a file is
in use.
4) I close Outlook 2007 (Task Manager says it is gone).

Try waiting a littly longer, say a minute or two, at this point before
continuing.

5) I eject the USB Flash Drive.

6) I insert the USB Flash Drive.

7) I launch Outlook 2007 under Vista.

8) I OPEN the Outlook Data File on the USB Flash Drive:
Outlook complains that it was closed improperly the last time used
and goes of to a lengthy check process.

Does waiting a while after cloing Outlook make any difference?

This is repeatable time after time.
This does not happen under WinXP/Outlook 2003.
This does not happen with other data files.

NOTE: delayed writes for the USB Flash Drive are disabled (Optimized
for Quick Removal under Vista).

Experiment with these settings a little to see if it makes a difference.
--
Brian Tillman [MVP-Outlook]