This wan't "my" post, but it decribes the problem well:

I am using Pan for large binary downloads and I have found a very annoying
behaviour when working with multiple servers. Let me explain:

Some servers I use offer a free account but with daily download limits,
and some others are not 100% time up. When I am downloading stuff from
some server and it fails (or just rejects my connection due to daily limit
reached) pan shows an error window reporting that was "Unable to connect
to server XXXXX" and it automatically goes to disconnected mode for all
servers, making the use of alternative servers impossible.

I would like Pan to be "wiser" in this situations and just go and use
other servers silently. Maybe it would be a good idea to mark the failing
servers internally in some way just to not try to connect to them in some
amount of time but never stop the queue when there are alternative servers
to download stuff from.

The server response when the daily quota has been reached is:

502 news.XXXXX.com: Access denied to your node

Also usually try "test servers" that usually are up and down, or sometimes
returning "502". IMHO Pan should handle these errors in a "non-critical"
way and don't go to offline mode so quickly.

Thanks a lot for your time and nice program