Please remove Adobe AIR and Adobe Muse completely from Add/Remove Programs (WindowsXP) or Programs and Features (WindowsVista/7).
Then restart the machine and install AIR 3.3 from http://get.adobe.com/air.
Once that successfully installs, if you are a subscriber, install Muse from the Adobe Application Manager, or else download the installer from http://www.adobe.com/go/trymuse. You can also use the trial installer if you are subscriber. You can always activate Muse using your Adobe ID during launch.
Hope that helps.