David,
Yes, you can disable the Password Manager. See this page for a how-to on customizing preferences:
http://kmeleon.sourceforge.net/docs/custompref.php
and this page for a list of preferences including the one for disabling the Password Manager. It's in the security section.
http://kmeleon.sourceforge.net/docs/mozpref.php
If you have any questions, let us know!
Andrew