iMovie and MobileMe Gallery: Some movie names may not work in MobileMe Gallery
Symptoms
Using certain characters in your iMovie project names or movie titles may create issues with movie display or playback on your MobileMe Gallery.
In some cases, the movie displays the message "QuickTime is unable to play this movie. Please try again" as shown in Figure 1.

Products Affected
iMovie '08 (7.x), MobileMe Gallery, MobileMe
Resolution
Avoid using the following characters in the iMovie project name or the published title in movies that you publish to a MobileMe Gallery:
If you do publish a movie to a MobileMe Gallery and it doesn't appear as expected, change the name in iMovie and then republish the movie.
Additional Information
See Final Cut Studio: Best practices when naming projects and assets for related information.