Not quite sure. I would try to empty all temp folders. Uninstall the old Air, then try to install the latest.
I am not able to uninstall the current version of Adobe Air. There is nothing in Add/Remove programs to use for uninstalling. I think there should be something there and makes me wonder if the installation is corrupted somehow. I wonder if there is some way to clean out the old installation so I can move forward with the upgrade.
I was able to fix my problems by using the Microsoft Fixit utility at
After uninstalling Adibe Air with the utility I was able to install the latest version without any problems.
I got the idea to do this from this post: