Viewing window problem

hi,

with reference to the viewing gallery help as found in http://www.kirupaforum.com/forums/showthread.php?t=58382

I have some problems. For example, on frame 26 i have 3 layers with keyframes as found in the attached zip file. it works fine. however on frame 30 of the same 3 layers, i wanted to have another photo gallery. When i clicked on the thumbnail of frame 31, the center viewing window, instead of expanding to show the picture, shrunk to a small rectangle and no picture was shown. (i am sure the required picture files are in the same folder as the flash file)

What was more puzzling was that i did the same thing on frame 27 and frame 31 and there is no problem.

What could be wrong?