I think you will find that this is an automatic function... this usually takes place for one of two reasons.

The host has reached it's bandwith limits and can service no more peers for the time being.
-or-
You are already downloading X # of files form a host and the host has a number set for the max number a single peer can download at one time.

In either case being Queued is good since it means you are in line and not being denied access.