The "no matching video" error can occur without warning in iMovie, and can prove particularly frustrating when you have already used the clip previously!
Problems with iMovie?
With iMovie Apple Mac owners have one of the best home movie editing suites at the fingertips. Available as part of iLife, iMovie enables users to edit video clips recorded on a digital camera ore imported via a video capture device. It’s ideal for making professional-looking edits of home movies and can be used to add titles, add transitions, and add a soundtrack.
Even the most perfect applications fail to work correctly every time, however. Some users have reported a “no matching video" error when trying to work with certain clips after they have been imported into iMovie. This is a common problem that can be resolved in the following ways.
Resolving the “No Matching Video" Error in iMovie
Commonly the error manifests without warning, and can occur with clips that have previously worked without a problem. The first thing to try is to check the video clip in QuickTime, to confirm that the clip does indeed still work.
Once you have done this, check iMovie to confirm that your clip appears in Movies > iMovie Events. With these two things checked, things will start to get a little bit messy as you need to persuade iMovie to reindex the clip.
Becuase the clip itself is fine - you've tried it in QuickTime - the problem is with the iMovie database, and you can resolve this problem by forcing the database to reindex your movie clip. There are variations on this, but the easiest way is to drag the folder or files from Movies > iMovie events to your Mac's desktop, then reimporting the video. Once the video has been reimported you can then drag the folder back into iMovie.
After this, close the app and restart it, and your video clip should have been successfully reimported, indexed and ready to use.
(Image via brynmawr.edu)
Install New Codecs
While a corrupt or faulty iMovie clips database might have been responsible for this problem, there are some other causes, such as a hard disk drive that is running out of space and incorrect QuickTime codecs.
You might be likely to experience a problem with the wrong codecs if you're importing video clips from a new camera that hasn't previously been used with your Mac.
If you suspect that codecs might be the problem, in Finder go to the Library directory on your Mac's hard drive and find QuickTime. In this folder, find and remove and file that does not begin "Apple". You might store them in a different folder, and replace them one at a time in order to trace the codec causing the problem, but as long as they're all removed you should find that the “no matching video" error no longer occurs.
Failing all of these fixes, however, you're faced with one last chance - if your Mac is suitable, upgrade to the latest release of Max OS X and purchase iLife 2011!