I have SE NC 9.421 installed on my go 750 when I play some music from my iPhone (iPod control cable) I got some "cracks" and "plofs" trough my speakers. Not loud but you can hear them. I also tried some other NC' some have the problem some don't. It seems like only the newer NC's have this problem. Like 9.051 doesn't have the problem. Then I installed 9.405 and 9.421 both have the problem. Back to 9.051 again no problem.