For SMF 1.1 and Joomla 1.0.x/Mambo 4.5.x, you should be using this:
http://www.simplemachines.org/download/index.php?thanks;filename=smf_1-1_joomla_1-0-x_bridge_1-1-7.zip
Joomla 1.5 has major changes that will not work with this bridge. I am working on a bridge to integrate SMF with Joomla 1.5.