Sidekick 2 - To-Do dates stop working end 2005 2

All sorts of funny dates appear when you try to set a due date after 31 Dec 05 - then you can't get rid of the funny date, and every time you try to do so, you lose part of the to do action - eg. if you have 'start school', it becomes 'tart school' and then when you try again it becomes 'art school' etc

Anybody got a solution?