error -2041: an invalid sample description was found in the movie

you are fantastic, this solved the issue with an .mp4 i was trying to play in vista 64bit

Ok guys heres the deal, if any of you are running XP then your in my boat.
I had a problem with this and read all your theorys, the good and the bad. Some of them actually do sound like theyd work.

But....

Just change your default application that opens MP4s (Im running the CCCP codec pack btw). I changed mine from quicktime to windows media and they work great. Also i guess you could get Media PLayer Classic as an alternative if you dont want anything to do with windows.

wow i wish i had time to do these huge multi step solutions....

I've got the new Samsung Pixon M8800 and it exports files with the .mp4 extension and this error happens to me too.

When i change the extension to .3gp the video file works, Bonus

Still need to use isquint though to convert it back to .mp4 file for imovie to be able to read it.

Just download Super2009 Video converter, it's free and converts all files to all codecs...

Just import the MP4's and export them to, lets say AVI.

It worked for me... Playing them now..

I've had the same issue for awhile now. This solution works about 90% of the time. I use VLC and stream the file to mp4v scale 1 and mp4a @ 192bits w/2 channels. The problem doesn't seem to be the video. It seems to be the audio. Most of the time, I can transcode the audio down to two channels and it works fine.

For cases where it can't open the movie, the problem is a little different. I had taken video and put the video in Divx format. Quicktime doesn't do divx out of the box. You can download a divx codex and play divx or transcode to something Quicktime uses.