Unlike QuickTime Pro 7, Apple’s new QuickTime Player 10 has lost its ability to capture and export individual movie frames. One solution is to use Google’s free Picasa
After downloading, installing, and launching, Picasa will will search your hard drive for all media files, including movies.
Use the sidebar (or search) to navigate to the desired movie. There’s also a movie filter at the top of the window.
Double click your movie and it will start to play. Pause the movie and use the time slider to find the still image you want.
Click the “Take Snapshot” button. Your frame image will be stored in the folder: Pictures > Picasa > Captured Video