You have probably installed updates for optional paid plug-in or other software that was not included with the particular product that you purchased. If you have installed other software, see the page linked from the iLok Authorization Info link on the right side of the Support section:
http://www.digidesign.com/support
Near the top on that page is a link to this page:
Pop-up Authorization Messages - Trial Licenses - Removing Optional Plug-Ins & Software
http://www.digidesign.com/index.cfm?...4&itemid=19348