Problem with Image Display in DirectRT

I have created a DirectRT input file in which multiple images are displayed in a change blindness flicker task. I converted all 60 images to .bmp files using image conversion software; all images properly display except for 4. I tried reconverting the images and re-entering the stimulus information in the input file, to no avail. I've created an abbreviated input file to illustrate this problem (attached). It includes the 4 images that are not displaying correctly as well as 2 images that are. I can't figure out what is different about these 4 files or how to correct the problem.

Thanks so much!