Grabbing a still frame from an iPhoto video

I took a video with my iPhone 5.

I imported it to iPhoto. Version 9.4.3.

I want to grab a frame from that video and use it in a calendar.

I read an instruction to export the movie from iPhoto and view it in Quicktime. From there I can export an JPG file with the frame.

I tried that but I can't see the video in Quicktime. I can see a preview of it when I push the spacebar from Finder. However, when I open the file Quicktime only shows a black screen. The movie progresses as shown by the progress bar at the bottom, but there's no video.

Any ideas what's going on?

I would bypass the iPhoto import. Just download the video on to your desktop and then play it in QuickTime from there.
There are a number of ways to import it on to your desktop-- probably the easiest is to just go to iCloud and download it from your photo library there. Assuming that the video was shot in the Apple native camera app.

Quicktime movies are not strictly frames they are, progressively generated on the difference of the screen.

Wherever you see the movie, let it run and stop it with the spacebar to get the frame.

You can nudge it forward with various combinations of the arrow keys and the shift, option, command keys.

To take a screensnap hit command shift 4 and drag over the area you want.