I love hearing feedback from folks running the software, even when it's to report that the program isn't running correctly. You can see some of the frequently asked questions here. If you run into one of these issues I hope the suggestions below are helpful.
It's funny, back when I wrote this program most digital photos were pretty low resolution and there weren't very many of them. Nowadays, high-resolution digital cameras are everywhere and people snap digital photos faster than ever before.
Several have written to report seeing an error attempting to save a medley image, after seeing the medley created successfully in the preview. Usually it's "Parameter Not Valid", but might also indicate a shortage of memory.
Usually this has one (or both) of two causes: a very large number of digital photos being used in the medley, and/or the digital photos are high resolution. Fortunately, you should be able to get good results with two workarounds:
Some have written to report that the program stops running before it has finished loading all of the images for the medley. Sometimes this is accompanied by an error indicating "path not of legal form."
A common cause for this is one or more "rogue" files in the folder tree being referenced for the tile images.
The workaround can unfortunately be somewhat tedious - you'll have to try generating a medley with different subsets of the tile images until you are able to create a medley successfully. Once you do, you'll know that the rogue image is in the set you didn't use for the successful medley.
The "library" feature might help here also - it scans the tile folder tree and loads each image in the process of creating a tile library. This process should halt on the same rogue file, and by looking at the tile library that it creates you can estimate the location of the rogue file based on how much (or little) of the original files made it into the tile library.