OK, I figured out that it is not really a log4net issue. I made a change elsewhere in my code, changing this line of code:
RemotingConfiguration.Configure(null, true);
To this:
RemotingConfiguration.Configure(null, false);
and data started flowing. I'm not sure what extra code I would have to write to get the "secure" version of remoting connections working, but any machine we would do this on is already behind the corporate firewall, so I may not have to fuss with security.
Thanks, Peter