I haven't had a chance to try some of the suggestions posted - but, found a cool thing yesterday (thanks to MacWorld magazine)
On Leopard, you can open a quicktime movie (using the space bar preview thing), pause on the frame you want, click with your mouse on the picture and drag it to your desktop, and viola, you have a still of that frame. All I could say when I tried that out was "go figure!"
I did have to right-click and select "open with" "photoshop cs3" to open the file, as it didn't have an extension identifying it as a certain file type (jpeg etc)
I also discovered by accident that if I dropped a clip into a 720p timeline, the stills I exported were the right shape and did not need the deinterlace filter applied.
So, I guess it all boils down to many ways to end up at the same destination
