My Nikon D40 lens won't adjust?

My Nikon D40 lens won't turn to adjust to a different millimeter. Any ideas why?

The little gnome inside is on strike because it wants a dental plan
You forgot to fill it up and now it's out of millimeter
Or… You dropped it or bumped into something

It could be broken, something could have gotten stuck. I suggest you remove the lens and carefully clean the contacts with a q-tip. Check if all moving parts work and put it back on it probably works again then.