Help needed: bizarre voltage readings

Feeling that my system can sometimes sound a lot worse than usual, I got a voltage meter to check if something was wrong with my AC power. Imagine my surprise when I found that one of the receptacles measured 122V between hot and neutral, 4V between ground and neutral, and 4V between ground and hot. HOW IS THIS EVEN POSSIBLE? If hot and neutral are 122V apart from each other, they simply cannot both be 4V away from ground, right? I tried taking the readings several time and they didn't change.

I tried the meter on several other outlets, including a couple that are on the same circuit as the problem outlet, and they all measured okay: 120-122V between hot and neutral, 120-122V between hot and ground and 0V between neutral and ground. So at least we know the meter is okay.

Please help. I'm really confused.