my update says invalid certificate and will not be installed?
My computer won't let me do an upgrade for itunes....I get an error message that says it's an invalid security certificate and won't be installed.
iPod shuffle, Windows XP
That suggests that the installer is getting damaged during the download.
I'd first try downloading an installer from the Apple website using a different web browser:
http://www.apple.com/itunes/download/
If you use Firefox instead of IE for the download (or vice versa), do you get a working installer?