Download and install this fix, without Windows Mail not running:
http://support.microsoft.com/default.aspx/kb/941090
Although it's labelled as for mail stuck in the Outbox, it also works
in other folders. If you don't know whether to use the 32-bit version
or the 64-bit version, try the 32-bit version first. If you have certain
common antivirus programs, such as most of those from Norton or
McAfee, or a recent one from Trend, remember where to find the
fix as you are likely to need it again, although not immediately.