The problem is in the function
add_plugin. It has a line
$plugin_array['toggle'] = plugins_url.'toggle-box/js/mce.js');
This does not work. Under 3.3.1, it needs to read:
$plugin_array['toggle'] = plugins_url('js/mce.js', __FILE__);
This probably is not truly the way this should be mended, but at least it gets the plugin to run again.