Are you sure you have started the correct version?
Have you uninstalled the old version first (I guess not)?
What was your previsou version?
When you install Windows Live Messenger it installs itself in "
C:\Program Files\Windows Live\Messenger", whereas the 'old' version installed itself in "
C:\Program Files\MSN Messenger".
So you probably have just started the wrong version (eg: by using a shortcut to the older version).
If that is the case I would suggest to uninstall the newest version again, then uninstall the old version. Only then reinstall the new version.
/ 
