Such problems are often due to interference from an antivirus
program. What if any antivirus programs do you have, and
have you ever had a Norton or McAfee antivirus program on
that computer?
For a temporary fix, download and install this hotfix, with
Windows Mail not running:
Although it's labelled as for mail stuck in the Outbox, it also works in
other folders. If you don't know whether you have a 32-bit version
of Vista or a 64-bit version, try the hotfix for the 32-bit version first.
The Vista SP1 update contains this hotfix and more, but takes longer
to install.
