glad to pay back (forward?)

Yes, the message means that quicktime can't get the coder/decoder that was used to create the file (called the "codec"). This is a problem with what I call "the media wars" over who can dominate the code used for all sorts of media. They try to lock us in to one kind: we just get confused.

Luckily, there are at least two other free players, vlc and mplayer that can often work when quicktime can't.

Here are the links to download and install the players for OSX. Once installed, you can set these with the Get Info trick and see if they work.

for vlc
for mplayer