What you have is a floating ground. Yes, this is a potentially lethal problem, and you should get it checked out and fixed by someone that knows what they're doing.

What if I have a voltage between ground neutral?
Looking at the product page for Nikon lenses, I notice a distinction between telephoto lens and zoom lens.

What is the difference between the two?  Why would I want one over the other?  I wiki'd telephoto lens but remain confused about this distinction.

Please talk to me like I'm stupid. :) I am hoping for a completely lay explanation.  In particular, I'd like to understand in what situations I'd use a telephoto lens, and in what (other) situations I'd use a zoom lens.
