Use getframe and movie, but get truncated movie...

• Hi, I have a problem using imshow + getframe + movie.
• My purpose is to put a square onto each white beads in the image, and assign a number to each bead.
• The Code, basically, use a loop to make every frame (512x512x3).And then use imshow+getframe to make a single frame. After the loop, put all frames together using command, movie.
• The problem is: I can see that images are 512x512 during the loop, but images get truncated (few beads lost in the upper part) in the final movie.
• Below is the link to the images: https://picasaweb.google.com/113057351208105452923/PublicPictures
• And here is the code (simplified):

F=moviein(n_frames);
for i = 1:n_frames
    % Here is the function to find bead position...
and give the blue, square frame
    [rc, row, col, singleImage]=positionWeighting(A,rc,i,nBeads,row,col,R);
    %
    imshow(singleImage);

      for j=1:length(nBeads)
          text(col(j), row(j), num2str(j),...
              'Color',[1,0,0], 'FontSize', 20, 'HorizontalAlignment', 'left')
      end

      F(i)=getframe
  end
  movie(F)

• Thanks for your time, read through my question and answer.
• By the way, I also wonder if there's some method can accelerate the process. I used imshow in every loop, and it should be very inefficient this way...