When viewing items in column view, you have the option to display a Preview column, where a preview image of your image or movie will be displayed, along with some file info.

Sometimes, viewing that image will cause the Finder to crash. To fix this problem,
delete the Finder Preferences, located at:

/Users/yourusername/Library/Preferences/com.apple.Finder.plist

Finder column view showing a preview of a quicktime movie:

Thanks to Trevor on the MacOSXhints forum