Creating New Tasks

I have been using task for almost a year, but recently it will not save a new
task. It gives me a pop-up window error "Please save task order by clicking
Save Task Order on Actions menu. The view must not be filtered or grouped
for Save Task Order to be availalbe."

I've never used a "task order", but I do use categories to group my tasks.
What is the conflict and how do I resolve? Why would this suddently start
happening?

Hope