Problem with Max7219 - one LED always on

hello, i'm doing a project at the university using multiple max7219 to drive a bunch of leds connected to self-made matrizes. the first led matrix is running fine, but the second one is giving me problems. wether i connect it to the first or the second max7219, one led is always lit, even when i change the code to switch all leds off and then do nothing. that doesn't make a lot of sense to me, as i would have thought that when the arduino (it's a duemilanove, btw) tells the max to switch off all leds, no current whatsoever would reach the led matrix. somebody got an idea? help would be very much appreciated. ^^ meht