Solution 1
Uninstall any copy/version of Adobe Muse already installed by following the steps detailed in Uninstall Adobe Muse.
To clear any remnants, delete the Adobe Muse folder:
Mac OS: /Applications
Windows XP: %programfiles% on 32 bit and %programfiles(x86)% on 64 bit
Windows 7: %programfiles% on 32 bit and %programfiles(x86)% on 64 bit
Download the latest version of Adobe Muse:
Mac: http://www.adobe.com/go/muse_latest_mac
Win: http://www.adobe.com/go/muse_latest_win
Install using the fresh installer downloaded from the links above.
Solution 2
Install the latest version of Adobe AIR from http://get.adobe.com/air.
Once successfully installed, reinstall Adobe Muse by following steps in Solution 1, above.