I am running Outlook 2010 (64bit). Every task in my To-Do list is duplicated. If I 'complete' one task, the second copy also marks as complete. If I flag an email to be added to the task list, 2 copies are listed.
I only have a single email profile configured on the laptop. I have tried adding an addition email profile, and that seemed to resolve the problem, but only until I closed Outlook and relaunched.