emg j bass neck pup white noise

[tedskank@hotmai]

hi there
i have been having some probs with my emg j bass pickups lately after not having any difficulties in the 3 years since i had them installed in my fender jazz. the neck pup starts to make a bad kind of rumbling white noise sound, but only after about 5 minutes of playing/being plugged in..so i turn down the neck pup and the sound is gone
I'm thinkin maybe the preamp has been cooked, but i can't think how i would have done that, and would like to find out so i can avoid this situation in the future!
i really like the sound that i get from this set combined with my flatwounds, as i play a combo of dub and jazz sounds, although it looks like i'll have to replace this set ( or the neck pup at least) and i'm starting to think of changin from emg to another brand that gives even more of that deep, fat yet refined sound.
any advice, ideas out there?
has anyone else experienced this bad sound?
thanks in advance for any help