So, you want to say that you added some word(s) into banned list, enabled plugin and after this, peoples still can make new threads/new posts with banned words ?
1. Make sure that you really enabled this plugin.
2. Check if plugin/hook system is enabled :
3. Maybe you have some others plugins, which are working with threads/posts too... (so there is some conflict)...
4. Did you added some usergroups or userid's in users exception list ? If yes, then check your usergroup and(or) userid - if you are in exception list, then plugin will ignore you - your account will not be checked, so you will be able to add even banned words...
P.S. As I wrote in second message - I am already tested plugin on vb 4.1.1 - so it must works...