I had the same issue but i got it resolved by cleaning the registry. You would need to follow these steps: First of all uninstall the yahoo messenge and restart your computer and than follow these steps:
Hit the windows button and go to "run''. you would need to type "REGEDIT" and hit enter. It will show you the registry of your computer. You would need to choose "HKEY_CURRENT_USER" hit "Software" go to "Microsoft" click "Windows" than go to "CurrentVersion" and hit on "Internet Settings" there you will see "Zones", there you will get to see some folders 0 1 2 3 etc, delete them. Restart your computer and download the fresh copy of latest Yahoo messenger and install it, it will work.
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