Try here for a pretty indepth look at the D80's autofocus.

http://www.kenrockwell.com/nikon/d80/af-settings.htm

You were the one using the older lens. Here is a thread in the a forum on dpreview.com that seems to talk specifically about your problem

http://forums.dpreview.com/forums/read.asp?forum=1034&message=27714295&q=d80+hunt&qf=m

"P.S. Most of your existing Nikon lenses will mount and work to some extent on the D80, but you are likely to find them cumbersome (unless you have specialty lenses such as macro lenses). Older AI and AI/S lenses will not meter on the D80, and that is a real pain. You can manually focus them, but DSLRs have smaller, dimmer viewfinders that make MF harder and they don't have split prisms, etc. to help you focus. Older AF lenses will meter and AF on the D80, but you will often find them to be slow to focus and the focus will hunt or fail to lock on as well.

Lenses older than AI or AI/S should not be mounted on the D80 as it can damage the camera."