"Do the videos work after they've been completely downloaded?"


If they work fine after a complete download, then my theory is incorrect.

Taken from Rosetta Help:

"The Fix Command: Correcting Problem Movie Files
The Fix command allows certain types of movie file problems to be corrected. These problems are often found in movies downloaded from usenet and other places. A standard file dialog is shown allowing the movies files to be fixed to be selected. After clicking on OK, one of two things may happen. The program will first check to see if each selected file seems to be a CDXA format movie file. If it is, it will try to create a new MPEG file that has the CDXA header data removed. Otherwise each file (assumed to be a combined MPEG file) will be split into its constituent movie files. The original files are never modified or moved. If the combined movie file was named ?movie.mpg? and consisted of three joined movies, the result will be three new movie files named ?movie.mpg-1?, ?movie.mpg-2? and ?movie.mpg-3?. Using a QuickTime movie player you should be able to play the new movie files in their entirety. If the movie file you try to split contains just a single MPEG movie then no new files are created. Also note that the original file must be a true MPEG file, and not a QuickTime movie file containing MPEG movie data. The latter kind of file can not be resplit using Rosetta.

Unlike the other features provided by Rosetta, resplitting combined MPEG movies and removing the header from CDXA movies may not always work. The original movies may not be in the proper format, or may be corrupted or be missing data, or otherwise not in a form that Rosetta can handle.