I have a problem with BrawlBox. Every time i import a image, even when the image's resolution matches with the image i want to replace, it always gives me a error. I use BrawlBox 0.78(also the latest version) and i edit my images with paint.net. I also save my images in PNG format. Any help would be useful.
What image are you trying to import in? If it needs a transparent background, paint usually doesn't export that way and you might need to use gimp.
Try to use a different BBox version. 0.78 is fairly buggy.