When you have todo items already set with a non-default priority, and edit a todo item, it changes the item to default priority without being asked to. For example, if I have an item set to priority 1, and want to edit it, when I bring up the edit box, the priority listed is "5" instead of "1". If cancel is hit, then no change is made, however if "Ok" is pressed, wether or not anything was changed, the program changes the priority to "5" needlessly. It is incredibly annoying.
Sending upstream
Upstream developer just fixed it - two-hour response time is pretty good. ;-) Anyway, next version of the Red Hat package will have the new version of gnome-pim with this fixed. Bug should be closed at that time.
Long since fixed apparently (also, it appears gnome-pim is considered a dead module, replaced by Evolution)