There is a button in the preview window at the top just to
the right of the preview quality pulldown. If you put your
mouse on it the tool tip says "copy snapshot". What It does
is places a copy of the current frame on the windows
clipboard. However, I didn't see any way to paste it to the
timeline from there. So I had to start photoshop, and paste
it to a new document, then save it, then open it in the
explorer window, then drag it to the timeline. Whew!