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Sometimes, updates simply dont update smoothly. Thats usually a sign you need to uninstall and reinstall the program.
So thats my first suggestion, go to your control panel, programs and features.
Uninstall combofix.. Once its removed. Restart the computer, and then download the newest version of combofix ( which should include the update ) You can get the newest version released March 19th here http://www.bleepingcomputer.com/download/combofix/
Once downloaded, install it. And you should be good to go.
Let me know if you get stuck, or run into any issues.
I strive to provide great service, and greatly appreciate a rating of excellent ( 5 stars ) selected and submitted below this answer or at the top right of the screen. I always answer follow up questions.Dustin S.Senior Technician and Network Switching Systems Operator / Maintainer.