I was getting this error message when Calendar Sync started and then it would crash. Looking at the boards I see several others have run into this also. I found the solution to my issue and I thought I would share it here.
In my case, the problem was being caused because I had installed Outlook 2013 and then had to downgrade to Outlook 2010 because of our Exchange server. When I uninstalled Outlook 2013 it left a registry entry behind. When Calendar Sync starts up it looks for,
I assume, the latest version of Outlook and it would find the registry entry for Outlook 2013. Even though that entry was completely empty, it seems to have sent Calendar Sync off looking for Outlook in the wrong place. Deleting that entry got Calendar Sync
to find Outlook 2010 entry and then it was happy.
A more complete description and instructions can be found here.
I hope this helps others having the same issue.