If you're referring to the "Active Topics" link not producing any results under 3.0.6 where it previously did under 3.0.5, then please have a read through this topic:
http://www.phpbb.com/community/viewtopi ... &t=1875595
Take special notice of this post
and this post
It gives an explanation of why this is happening and how you can get the Active Topics link to work like it did under 3.0.5.