Just putting a quick tip out there:
I was teaching a workshop this past weekend and got frustrated when a student's movie was not previewing correctly during playback. The still photos showed up fine, but any video clips would not appear at all. The clips had been rendered but still they didn't show up in the Canvas window during playback.
My co-facilitator figured it out: the caps lock key was activated on the keyboard. For some reason, the clips wouldn't preview with caps lock on.
Lesson learned. Check the caps lock key first. :)
