I am having the same error message upgrading Adobe AIR 3.8 to 3.9. Fully patched and up-to-date Windows 7 Ultimate 64 bit. Windows Installer Service is verified running. Logitech proceses have been stopped. Antivirus program has been paused. That exhausts all the solutions I can find on the web! I have another computer with the same OS that is not having the problem ... hmm.