Vista - Downloads disappearing; cannot save attachments.

I had my wife's account set up as Administrator. I set it back to standard
user. Since then, whenever we download a file through IE7, it seems to work
(downloads to 100%), then the dialog disappears, and the file is not in the
target location. It seems like it gets moved, since if I download to the
Desktop, I see an icon, that then disappears. Restoring the account to
Administrator did not resolve the problem.

Downloads through Firefox work correctly.

We do not have Norton or McAfee installed. We have AVG. Uninstalling it
did not resolve the problem.

In what I think is a related problem, we cannot save or open e-mail
attachments from Windows Mail. (I have unchecked the "do not allow download
of files that may contain viruses).

Disabling User Account Control resolves the download problem, but not the
attachment problem.