cann't you just invert the code, so when the led should be on, you write them to low,.... just a short idea, with out any real thinking ,...ahhmmm...
...I just checked by putting a led on another's leads but reversed and unfortunately it appears to be working.
Will someone please come up with a better reason why its not working so I dont have to desolder that many LEDs?
It still doesn't make sense to me that LEDs which are wired the wrong way light up at all, but well ... you proved it!??
You probably solved some "MAX7219 Mysterious Light-Effects" postings, because you are the first one coming up with an explanation for the problem.
I'm going to build a small "Not-working-inverted matrix" over the weekend and see if I can make sense of the whole thing.