I recently bought a cheap, POS guitar for the sole purpose of messing around with it, as far as modding and stuff (practicing before I do it for real on one of my good guitars). It's a Harmony Les Paul style, and I put different pickups in it that were pretty hot (around 13k in the neck and 14k in the bridge). I didn't notice it when I first switched them out, but now I've got an annoying hum that only subsides when I touch the metal cover on the cord (doesn't go away when I touch the strings). The jack is nice and tight, and the cord has no slop or anything inside the guitar. None of my other guitars do this, so I think that eliminates the possibility of it being the cord itself causing the problem.
The pickups (humbuckers) that I put in were pretty beat up looking, so I cleaned them up with 0000 steel wool and buffed them to make them look nice. So, do I have a ground problem, could it be that steel wool fibers may be the culprit, or something else?
Hey, by the way, cool forum! I don't even know how I found it, but I'm glad I did!