The errors happened in different version of matlab on the same code

As I posed before, http://www.mathworks.com/matlabcentral/answers/37417-how-to-get-the-value-of-a-certain-pixel-region-in-video-and-analyze-them runs well in matlab version R2009a.However, it goes wrong in version R2010. What was the problem? Thank you very much.

ps: original code is

%read the video
      avi = aviread('sample.avi');    
      video = {avi.cdata};  
      pixels = double(cat(4,video{1:end}))/255;
      nFrames = size(pixels,4)
    %convert the video to gray scale
    for f = 1:nFrames           
      pixel(:,:,f) = (rgb2gray(pixels(:,:,:,f))); 
    end
    background=(pixel(:,:,1)+pixel(:,:,2)+pixel(:,:,3))/3;   %get a background picture
    %transfer the video to binary video and counting
    for m = 2:1:nFrames          
      dif=(abs(pixel(:,:,m)-background));           
      bw = im2bw(dif, 0.2);  
          if (0==any(bw(:,314))) && (0~=any(bw(:,313)))
           n=n+1;
          disp(n)
          end
    end

[Wayne King]

You should provide the error messages

[Walter Roberson]

Or if there is no error message, describe the difference between what you see and what you expect.