The Movable Type manual leaves much to be desired, but the good news is that there is a web site on Learning Movable Type which had an excellent article on using suexec which my web host recently startedd using. All of this comes up because of a bug in PhpBB which allowed for the defacement of this website, because all of the webpages were world writable.
Problems now fixed. Response time of the web host? Seven minutes flat for a four paragraph reply which actually made sense.