I have it set so that people under x amount of posts can't post or view in certain forums using the forum hack.
I also have the Last Post thread hack.
Users can totally bypass the "can't post if you don't have x amount of posts" by clicking on the Last Post thread link.
Kind of defeats the purpose
look:
http://php.stileproject.com/spf
try posting from the forum link then last post to thread link.