Hi
The BFA Popular posts from category widget is not working for me, the widget isn't even showing up the widget title in sidebar
any idea what can be the problem?

what release of atahualpa and wp?
What is the url?
what sidebar do you have it in?
Have you any other widgets?
Did you disable all your plugins to see if there is a conflict?
If the widget is in the right sidebar, did you look to see if the last paost has any formatting from WORD that can screw things up?