I found a small bug with the program today. After looking at the sample mabster posted yesterday, I reorganized my collection a bit. I placed all of my cover images in a folder, to quickly move between PCs, so I don't need to worry about the path being different from PC to PC. C:\Madprops\Covers\ is the location I chose. After I moved the collection from one PC to another, I opened the file, to notice no covers would show. I thought there was a typo, and tried to reset the backup PC to re-point to an image. It still would not show. The only way to get a backup copy to show an image, is to select a different image, and then back to the original.
Seems to be a bug with how comicster is caching the thumbnails, or how it refreshes it. I checked the sample mabster posted, and I don't see a single cover in there either (and some of those point to a web URL).