Creating a Kwiki MT Plugin

I'm trying to build a plugin for Moveable Type that will allow me to use 
Kwiki formatting in my blog posts.

I've got an initial version, which works at 
http://aamcf.co.uk/mtplugins/Kwiki.2004-12-06.txt

Its based on the CGI::Kwiki plugin for MT[1] and the Kwiki plugin for 
Template Toolkit[2]. It works, but I don't understand why.

The problem is the line, which I added in my best cargo-cult style when 
something wouldn't work:

   sub Kwiki::Config::database_directory { 1 }

If it's not there when I rebuild the site, MT processes barfs with the 
following error:

  Can't locate object method "database_directory" via package
  "Kwiki::Config" at /usr/local/share/perl/5.8.4/Kwiki/Pages.pm line 128.

For some reason, if I try to rebuild individual entries without that 
line the first few work, then MT barfs again.

Anyone able to explain what's going on?

Andrew

[1] http://mt-plugins.org/archives/entry/kwiki.php
[2] 
http://search.cpan.org/~domm/Template-Plugin-KwikiFormat-1.03/lib/Template/Plugin/KwikiFormat.pm