QuickTime won't open any files and can't download the latest update

I have .qtl files downloaded, but when I click open, nothing happens. A pop up window tells me that I need to install QuickTime Player 7, but when I agree to install it, it says "Can't install the software because it is not currently available from the Software Update server." I've had the same results with multiple attempts over the last few days. I need to watch these files for school so I'd really appreciate any help.