I have QT Pro ver. 7.0.4 and operate with OS X 10.4.6 and QuickTime 7.0.4 seems to operate properly. I was notified that QT7.1 is available (3 times). I verify 'disk permissions' and try to upgrade but each time my upgrade was unseccessful with message, "digital signature for package is incorrect..." I tried just downloading from Apple site but get "warning" Following disk image failed to mount - Image: QTInstallerX / Reason: Invalid checksum." I get this message with both QT 7.1 and 7.1.1. Any input as to how I can correct this problem would be deeply appreciated.