I use FoCal to display three sets of widgets. I have just upgraded to WordPress 2.9 and while I can set 'How many Folding Category widgets would you like?' to 3 and configure those three instances in Setup FoCal, only a single instance of the widget appears to drag to the sidebar. Dragging that one then doesn't leave another instance to place on the sidebar.
I have uninstalled and reinstalled the plug in and don't think that I have forgotten anything.