User click on ads when they need something. When we talking about directory sites these are used by webmaster and they want only submit directory not a genuine content searcher. That is most important reason your visitor are not clicking on your ads.
Don't try to force your visitors click on your ads. You may be banned. Normally general people who even don't know about Adsense like programs are more likey to click on the ads. So try to get more general visitors.
It's not a blog! It's a directory. When your trying to increase your post count, as your doing, at least read the thread and see what it's about...
How about simply asking them to click on it? Oh and don't forget to be polite and say "pretty please?"