Make AVI file from plots?

Howdy folks- I've tried searching around on here for a few hours with little success. I'm trying to make a movie that will show the evolution of the surface over time. I've successfully graphed a colored surface of x,y,z values using pcolor - x and y are the coordinates, z is an interpolated elevation - and set up a for loop to run through my images, and put them into an avi file. The only problem is that when I open the avi file in VLC, each frame is black. I'm guessing it's something to do with defining the colormap in my avifile command, but I can't figure out how it works... any tips?

I'm using R2011a on a Mac, if that matters - I know that means that I don't have any options for compression type.

Thanks! Code is below.

-Sam

    clear all; close all; clc

    load WSE_0524-0703.mat

    aviobj = avifile('test.avi','compression','None','fps',1,'quality',100);

    x = easting;      % x coordinates of wells
    y = northing;     % y coordinates of wells
    xDim = 305100:25:305650;    % define dimensions to interpolate
    yDim = 4793600:25:4794200;  % define dimensions to interpolate
    [gridX,gridY] = meshgrid(xDim,yDim);    % make a meshgrid of x and y

    z = wseAll(1,:)';
    F = TriScatteredInterp(x,y,z);  % interpolate between wells
    gridZ = F(gridX,gridY); % solve for z at each point on meshgrid

    colorplot = figure;
    pcolor(gridX,gridY,gridZ);  % 2D meshed surface colormap
    hold on
    shading flat    % turn off grid
    colorbar;   % add colorbar
    caxis([295 300]);   % colorbar scale
    hold off

    frame         = getframe( colorplot );
    aviobj = addframe(aviobj,frame);

    for k = 2:300:902;
        z = wseAll(k,:)';
        F = TriScatteredInterp(x,y,z);  % interpolate between wells
        gridZ = F(gridX,gridY); % solve for z at each point on meshgrid

        colorplot = figure;
        pcolor(gridX,gridY,gridZ);  % 2D meshed surface colormap
        hold on
        shading flat    % turn off grid
        colorbar;   % add colorbar
        caxis([295 300]);   % colorbar scale
        hold off

        frame           = getframe( colorplot );
        aviobj = addframe(aviobj,frame);
    end

    aviobj = close(aviobj);
    close all

[Image Analyst]

I don't have MATLAB on our Mac. For reference, there's the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_create_a_movie_from_my_MATLAB_figures.3F