"Unable to Save your Message as Draft error" happens every time the
auto download mail happens. Don't hit Get Mail while you are writing,
and set your Tools > Account Settings > Server Settings > Check for
new messages every ... minutes -to-> 90 minutes or more. So that it
doesn't auto check while you are writing. If the "Unable to Save your
Message as Draft error" happens, you have to copy everything over to a
new email to send it, not a bug fix, but all I can figure out.