Thanks for the screen shots. As far as I see you don't have a problem with MED, you have a problem when opening certain images that you've created.

They appear without extension (.pcx) in your File Open dialog, however that can be your Windows setting, so make sure they have the correct extension and are indeed PCX. Attempting to load PCX files that have a wrong format, other than 8 or 24 bit PCX, can cause an application to terminate or crash when reading them.

If in doubt, use a different paint program for creating your images, and/or use BMP or TGA if your paint program has problems with PCX.