This Quicktime ver (10.3 I think) came with the OS. This is on a Macbook Pro with OS X 10.9.5. I think it just got damaged or corrupt and needs to be reinstalled. This is NOT due to upgrades, it was working but overtime it started developing problems. Needless to say I can not play any videos.
When trying to open, I get a 'Problem Report QuickTime Player' with options 'OK' and 'Reopen'. My default Quicktime Player that comes with OS X 10.9.5 stopped working.