I just had a look for you and the program seems to work fine When you input the filename of the picture which you are trying to load there should be a * at the end of the filename. This is because the disk loading/saving uses full 16 characters as the filename. Loading can simply be solved by adding * at the end of your filename.
I tried loading in two example Koala paint images from a Demo Makers/Creators Disk using this:
Filename 1: ?PIC A *
Filename 2: ?PIC B *
Nothing failed to load and the two images displayed correctly in the demo.