Problem with Custom Sprite

[GreenGiant]

So, I made a Blue Mage sprite, basically just combining Larg and Rofel, but when I attempt to import the bitmap, Shishi throws an error:
System.BadImageFormatException: Format of the executable (.exe) or library (.dll) is invalid.

With a bunch of other stuff. Can anybody tell me what's wrong with my .bmp?

[GreenGiant]

Ok, update, it's not just this sprite. Anytime I export a .bmp from shishi, modify it in GIMP and convert it back to a 16-color .bmp, it refuses to be imported back into shishi. Odd...

[GreenGiant]

Well, problem solved. Use GraphicsGale instead of GIMP.... Well at least it works, but now I have to start over...