iMovie '11 stopped playing some of my audio sound effects.

I had the same problem just happen! I deleted the audio (song that had the yellow caution exclamation point) from my video and then the rest of the audio started working normally. I've been able to edit and add 3 new songs with no problem. I read that if you keep the audio with the caution sign in your project it will start to corrupt the other audio files. Can't say I experienced it, didn't want to risk it so I deleted the song in imovie and on itunes. Hope this helps!

One other thing I've noticed, is that any audio I added to my movie project after the corrupted song (yellow caution sign) did not play. Once I deleted the corrupted song, I added the same files back in and they are working fine. It took imovie about an hour before the corrupted song I added, caused this problem.

The "yellow caution badge" that Peter refers to indicates that iMovie can't locate the clip, whether it be video or audio. The "badge" is in the shape of a yellow triangle enclosing an exclamation mark - see this picture:

One tip that may help is to delete iMovie's preference file. That file can become corrupted under certain circumstances, such as when iMovie quits unexpectedly or is Force Quit.

The file is located in your User (Home) folder Library/Preferences and, for iMovie '11, is named "com.apple.iMovieApp.plist".

Close iMovie, then drag the .plist file to the Trash. When opened, iMovie will create a fresh .plist file with the default settings, which you can change if desired in iMovie's menu item iMovie>Preferences.

Deleting the file will not harm your existing Events or Projects, but may fix iMovie's abnormal behaviour.

NOTE: I have seen similar behaviour myself, as you and Peter describe (but not as serious - it was on a test project). My fix was to check each and every audio track and switch Ducking OFF and ON (or ON and OFF depending on its setting). The disappearing audio suddenly re-appeared on the problem track. But it may have been coincidental, as I was playing around generally - perhaps something else I did triggered it.

John

This thread may help with the yellow triangle problem - thanks Josh (PixelRanger):

https://discussions.apple.com/thread/3062057?tstart=0

John

I knew i had some yellow badges so i just went looking for them.... low and behold, once i deleted the one bad yellow triabgle file the rest started to play correctly!!!

Same thing happened to me and I fixed it after I re-traced my steps knowing it was likely not an iMovie issue.

Problem was I moved a single audio file, that was referenced in my clip, from one location to another ... and iMovie did not like that one little bit, so iMovie did to me what it did to you and screwed the entire clip.

All you have to do is replace the audio file back to the original locaion on your disk that iMovie is looking for .. OR... delete that audio snippet and add it again from its new location.

You might not know what one it is so just go through your clip and as soon as you hear audio come back in (oddly for another clip) you've found the culprit.

Its an iMovie bug but, as a developer, I can see how they didnt account for it

I had a similar experience. Thanks for your post. It helped me fix my problem.

I have also noticed that if I don't turn off Time Machine in Preferences it will screw with iMovie settings. I create a lot of long narrated slideshows in iMovie so spend a lot of effort timing audio recordings to stills. I have noticed that there were times when these timing "tweaks" would not hold in iMovie - that they were getting messed up if Time Machine had performed a backup. Turning off Time Machine in preferences whenever I have iMovie open has solved this problem for me. iMovie had been doing crazy things like changing back transition timing that I had edited or undoing changes I had made using the audio clip trimmer. All these things stopped happening when I started making it a practice to keep Time Machine turned off whenever iMovie is open.