An acceptable version of Quicktime is installed
You should be able to watch the presentations hosted here without problem. The system will check now to see if your QuickTime version is current - if QuickTime Player opens with instructions, please upgrade to the latest version.
If you continue to get the "QuickTime Problem" indicator, but the checking system leads you to this page without launching upgrade instructions, then your installation of QuickTime is likely incomplete - perhaps you have accidentally deleted the QuickTime Player application. The presentations should work without trouble, but to stop seeing the "QuickTime Problem" indicator, you can reinstall QuickTime to give you a complete installation. QuickTime can be downloaded and installed for free from here.