I have had this problem on my machine once. maybe twice. Roxio acted up. I am told this happens because the installer information in the registry or on disk gets corrupted. I could still visit web sites & download stuff, fortunately.
attempt to uninstall the program. usually there's an uninstaller somewhere, either in the Start|All programs menu somewhere, or in the
C:\Program Files\directory under the company name or application name. you will need to close the installers first. try hard and long and use cancel a lot! If you can't, try the next step.
try the msi cleanup utility (mscuu2). this is a last ditch effort.
If step 2 doesn't work, try to close the apps down repeatedly until things are stable and then uninstall the apps that are running.
mscuu2/Windows Installer Cleanup Utility
download mscuu2 version 3 from Microsoft.