Thunderbird 3

I just updated my email to use Thunderbird 3.1 and it iis a real pain to use. Now instead of the next email loading into the window if Ii delete the previous one and the window closing when I get to the end of the folder I get a choice of either having to reopen the window for each individual email OR when it gets to the end of the folder it starts showing me emails over again that I already decided to keep and if I am in a hurry I end up deleting a load of wanted emails.

How can I make it stop at the end of the folder or is the only choice to dump Thunderbird 3 and reinstall 2.