Current leakage over HDMI?

I just noticed that I can get a small electric shock (only noticeable through thinish skin, such as my thigh)when touching the metal case of my laptop and the outer pole of the laptop's power adapter. The shock goes away when I unplug the HDMI cable leading to my TV. My TV is turned off. My laptop isn't plugged into anything else. With the HDMI cable in place, my multimeter gives highly variable voltage readings between my case and the outer pole of my power adaptor, up to a couple of volts (the numbers flash too quickly to be certain exactly what the peak is). Again, this dissapears when I unplug the HDMI cable. My laptop isn't plugged into anything else. What the hell? Seriously? How are these things in electrical contact? Does plugging in an HDMI cable ground my case to the house wiring via my TV?

If you are wondering why I noticed this, my power cord keeps falling out and landing on my thigh.