Please see chapter 12 in the book for instructions on how to clean out your CYD system at the end of the year.
This happens with some installations of Outlook. You can fix it by using a different symbol, try the # sign instead. You will have to change the search criteria for each of your context folders to look for the #context (#NA, #WF, etc..) instead of the @sign (@NA, @WF, etc..)
CYD is only supported on Windows today, I am planning to test it on Outlook for Mac, sometime this year (2015)
You can find step by step instructions on how to add the Query Builder tab in Outlook.