Adobe Air "damaged", can't run Rosetta Stone

I installed Rosetta Stone on my laptop (Windows 7 Ultimate) a few days ago and it was working fine until today. Now when I try to open it it says: "Adobe AIR. The installation of this application is damaged. Try re-installing or contacting the publisher for assistance." I have uninstalled/re-installed several times and it hasn't helped. One more thing: when I go to the start menu and type in Adobe Air, it doesn't show up, only the installer does. I don't know if that's significant or not (I'm not tech-savvy). Please help?