I started out just nailing frames and doing them one at a time. I now know better on both counts. Here is the voice of experience....
Nailing frames that way is guaranteed to have them pull apart. Frames can get quite heavy full of honey, and they get glued into the box by propolis so they have to withstand prying. Nailing into endgrain has no strength, and you didn't use glue either. Nail frames 90 degrees to the pulling direction. On the top bar, nail into the end bar under the lip, or into the ears (like you did). This gives some strength as the nail can't simply pull out, it has to break wood. The nail straight down into the top does nothing. On the bottom, nail from the sides through the bottom bar. Always use glue as well. It's stronger than any nail. Also, you'll wear yourself out assembling one frame at a time. Build a simple jig....
http://www.myoldtools.com/Bees/framejig/framejig.htmAnd buy yourself a cheap brad gun and a small compressor.