Are you checking files with Bitzi before download? If other users have rated the file then you'll see whether anybody else has had problems with it.
How to use Bitzi Web Lookup .. & How to use Magnet Links & Direct Connect/Browse/Chat

It shouldn't really make a difference if you're using Pro or basic. When a download gets stuck, right click on the file in the results window > search more > get more results. Or start a new search for the file, sometimes that can kickstart a download.