Richard,
this problem has been fixed in Pound 1.7. A current version of Pound works flawlessly w/ OpenACS including tDAV. Pound releases and the current development snapshot are available as tarballs from http://www.apsis.ch/pound/ or as a GNU Arch (http://wiki.gnuarch.org/) archive from the Code Mill (see http://www.thecodemill.biz/publications/blog/one-entry?entry_id=10095).
/Bart
