Unexpected error?

[mnsg]

yes, gimp can only index textures with a 256 color limit. anything else won't work.

Not completely true.  Try editing Donkey Kong and Diddy Kong.  Even though all of their indexed textures use a maximum of 256 colors, not all of them will work with The GIMP; you can edit them there, but you need Photoshop to index them properly.