Vista - Message Window Doesn't Open On Top

Hope to get some insight on this issue.
Windows Mail: When I double-click a message in my inbox, it opens the
message in it's own window, as it should, however, the message window opens
in the background only (underneath the active Windows Mail window). It
leaves Windows Mail window on top. So then you have to know to look for it,
otherwise you would think it didn't open the message.

Now, opening the inbox message any other way performs exactly as it should.
For example, highlighting the inbox message and clicking on File menu then
Open, will open the mail message in its own window, active and in the
foreground, just as it should. Also, if you right-click the inbox message,
then Open from the sub-menu, it too opens properly, active and in the
foreground.

Can anyone explain why this might happen? I'm using Windows Mail, Vista
Home Prem. I think this is a bug, and I can't figure out how to fix it.

Thanks, jb