I did some Outlook tweaking and tinkering this morning and noticed all of a sudden double entries for my task (to-do list) items. However if you try to delete one, both entries of the same task are gone. Weird, but there’s a solution:
Close Outlook and restart it by going to
Start -> Run then type “outlook.exe /resettodobar”
Once your Outlook opens up you should only see single entries of your tasks again.