Buzzzing problem

[Miracle Man]

Ok, here's the deal.

I did some tests today with my guitar and I'm not shure the "results" are normal.
The guitar is an SG type, the amp was a '77 Marshall Super Lead (no master) through a 4x12 and I used a ProCo Rat for distortion.
Here's what I noticed:
-When I touch an electronic device that is plugged in, such as a DVD player with a metal cassing in my case, I get this anoying buzz.
-When both pickups are on, the guitar is much more quiet and it doesn't feed back even if I stand in front of the amp. But when individual pickups are selected there is this humming. Not a grounding problem because it doesn't go away even when I touch the string or the bridge.

Is this normal?
Also, can someone explain guitar grounding to me?

Cheers, Troy

[Muzzzz]

are the humbuckers wired to do coil splits? that can make a 'bucker hum more than usual. also, other electric stuff (computers, dvd players) make pickups buzz a lot when you're around them, i've found. it's pretty normal.

Well that's all i know on the topic...