I can never leave well enough alone, so I removed the pickguard on my P/bass to have a look, and when I replaced it and plugged in, it's humming like crazy. Before it only had the normal amount of P/bass hum, but now . . . When I touch the strings, it goes away. While I had it open, and after it started humming, I shielded the cavity w/shielding paint, but that made no difference. I don't seem to have loosened any wires. Any ideas?