problem specifying port to ssh

[Don Cohen]

Here's the behavior I see:
 # ssh don at isis.cs3-inc.com date
 Thu Apr  6 14:19:16 PDT 2006
 # ssh -p 22 don at isis.cs3-inc.com date
 ssh: isis.cs3-inc.com: System error

These ought to be the same thing, since the default port is 22.
Whatever port I try to use (other than not specifying one at all)
seems to give the same problem.

This is on one particular linux (FC4) machine (2.6.15-1.1831_FC4)
 ssh -V => OpenSSH_4.2p1, OpenSSL 0.9.7f 22 Mar 2005
I don't see the problem on other machines, and in fact it seems
to be a recent problem even on this machine.  I don't think I've
changed ssh on this machine, so it's probably some other change.
The question is what could cause this.  If anyone has an idea of
what the change might have been that caused it, or how to fix it,
I'll be happy to hear about that too.

Please respond to me (as well as the list) since I'm not subscribed.