Now I can't save as QT movie and then try to open it like you did because the QT plugin under all three browsers asks me to pay for QT Pro upgrade, but I did try all three browsers with the link extracted from your movie screen,

http://pulsar.esm.psu.edu/Faculty/Gray/graphics/movies/g4_tanks_LAN

(pasted to each browser's location bar)

Safari: plays only the sound

FireFox: plays ok

Camino: plays ok

Then, I ask for the info on the QT player plugin, and in all three browsers it is the same, version 7.5. Well, they sure do not work the same.

And I tried Quicktime itself going to the above URL without any browser, and QT plays the movie ok directly (but again, wants me to buy an upgrade before allowing me to save).