Another way of doing this is to scrub around to the frame you want to freeze on. Razor the head of that section (this will leave you with the target frame and some additional frames to the right of it). Then, with the timeline on that new razored section, right-click and select "Video Options," then choose "Frame Hold." You can tell it to hold on "In Frame"--from that time forward, as you drag the tail of that razored clip, the frame will hold for as long as you drag it out on the timeline (note: you won't notice it while you're dragging it across the timeline, only during subsequent scrubbing/playback).