Evidently this problem is solved with the installation of the new Vista
Service Pack 1. I had the same problem, likely caused by my virus software.
My deleted folder would not automatically delete files there after closing
Windows Mail even though this feature was properly checked. Furthermore, I
could only delete a few messages in the delete folder manually before getting
the dreaded error message. I was strongly considering a change to Windows
Live Mail, when the new Vista Service Pack 1 came out. Also, I was getting
about 20 or more junk mail files every day despite using message rules for
certain words before the installation, now I might get only 1. It's scary!
The change after installation and restart was amazing. After installation and
restart, I tested Windows Mail by trying to delete over 300 messages in my
delete folder at one time. It worked! I also tested the automatic feature to
delete messages in the delete folder upon closing Windows Mail. That worked,
too! Thanks, Microsoft! Could it be that my Internet Service provider had
something to do with this as well? I don't know.