I can set up a ban in the typing window by writing:
/mode #channelname +b *!*@*.aol.com
for example would ban any aol user, I think.
The ban shows up in the channel modes window after right clicking. But when I leave that channel where I am op I find the ban is removed, and is not there when I re-enter. I tried putting it in the options/perform menu on start up, but that does not seem to be having any effect. So the question is: how do I make the ban stay when I am not in the channel. This is a channel properly registered with ChanServ.

Your going to need to /msg chanserv help or whatever and find out if the chanserv has a permanent ban feature and enable it then.

As far as i know if the channel is registered as you say, the modes should stick. Perhaps another user is removing it on you while you are gone? You may look into mode lock (Usually /chanserv set #channel mlock or /chanserv help set mlock for help). You might be abel to set soemthing such as:

/chanserv set #channel mlock +b *!*@*aol.com

Where a ban would not be able to be removed, nor another one place. If you know its not another user, you may want to find out the IRC software the server uses and look into how it runs. This can easily be done by looking in the status window while your connecting. At the top, you should see some form of greating such as "Welcome to <network>" and below it listing soemthing such as:

Your host is <server>, running version Unreal3.2-beta17

If all else fails, try joining #help or #oper. Those are usually designated channel for the operators of a network. You can try asking them why your ban would not stay.

Dunno if that works on any other network, but DALnet chanserv doesn't allow a MLOCK on +b

On Webnet, there is such a thing as /akick where ChanServ will automatically kick and ban the address as soon as it joins the channel. This works well when the ban list is lost due to netsplits or whatever. If you're a SOp or chan founder you could try /chanserv akick #channel add +b *!*@*ip.here

Same on DALnet, except we don't specify the +b there

/cs AKICK #channel add *!*@*dialupat.earthlink.net etc...

Works in Starchat.net