This is (somewhat) driving me crazy. Just like the title states, my chain rubs and makes a clicking noise from the rear derailleur, but only in one gear.

Details: 1986 schwinn, so friction shifting, 3 chainrings, 5 speed freewheel. In middle chainring (And top ring, have to admit now that I'm not sure if it happens in the low ring) the 23 tooth gear causes a rubbing/clicking on the chain. This only happens in this gear and every other is silent and fine.

The only hint I have is that the "hang" of the derailleur increases/lessens the amount of rub. IE: if I move the angle up/down it changes/increases the amount of rub.

So. First, what other information could I provide to solve this? I'm pretty new, so please forgive me for not using correct lingo or providing enough/correct info (I'm a tech support guy, so I know the frustration in that).

Second: HELP! It's maddening that I can't figure this out. I can't understand if something's bent (seems if that's the case, then why happen in only one gear?) or what?

Thanks!