I don't have a direct answer, but you might try downloading the trial of PPRO CC just to check whether it can open the "768" clip. Also, might be worth checking whether VLC will play the clip.
I'm not even sure what the ID number signifies. The data point that caught my eye in the clip that won't load in PPRO CS5 is "Format settings, GOP: M=3, N=12 or Variable." Don't know what to make of it, but I've never seen "variable" there.
