I ran into the same thing. I have no sophisticated graphics program at all, just plain old Paint. I found that if I change the artwork from color to black and white, I can then open the artwork in ProntoEdit (I assume that step is where you hear that you have too many bits per pixel).
I have no clue what to do if that is not it.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
