I just had to move my sub (HSU VTF2) out of the corner so we could get some window treatments installed. I put it back and I am hearing a hum now. I had this problem when I first got the sub and it was a grounding issue. I had to get an adapter to turn the 3 prong plug into a two prong one, plug that into the wall, and I was ok. We'll even though I still am using the two prong one in between, I am getting the humming noise again.

Any ideas?

try unplugging your television cable line if you have cable. does the hum go away?