apache error_log:
[Wed Sep 20 15:09:09 2006] [error] [client IP] (20014)Internal error: Can't open file '/usr/local/svn/guide/guide/format': No such file or directory
[Wed Sep 20 15:09:09 2006] [error] [client IP] Could not fetch resource information.[500, #0]
[Wed Sep 20 15:09:09 2006] [error] [client IP] Could not open the requested SVN filesystem  [500, #2]
[Wed Sep 20 15:09:09 2006] [error] [client IP] Could not open the requested SVN filesystem  [500, #2]

I know there is no such file, but there is not supposed to be.  webdav should redirect, according to svn documentation, through this piece of httpd.conf:

<Location /svn>
  DAV svn
  SVNParentPath /usr/local/svn/guide
  AuthzSVNAccessFile /etc/authz-svn-access
  Satisfy Any
  Require valid-user
  AuthType Basic
  AuthName "Subversion Repository"
  AuthUserFile /etc/svn-atuh-file
</Location>