commit-archive failing? SOLVED -- human error...

I have:

 config-management {
     commit-archive {
         location scp://cerberus:xxxxxxxxxxxx@mgmthost/home/cerberus/commits/
     }
 }

And when I commit, I get:

Archiving config...
  scp://mgmthost/home/cerberus/commits/  OK

But no new archive is appearing in mgmthost:/home/cerberus/commits/.

Any ideas?  The message says it's working, and I see the ssh logins, but...

Also, DNS resolution on cerberus — the "spare" ER-POE5 that has only its management interface connected at the moment and has its gateway address pointed at the other, active ER's management address — has mysteriously stopped working since last night.  I have not changed anything on the other router that should have caused it to stop forwarding, and DNS on the other router (the ER-X) is still working perfectly.

I even added a static /etc/hosts entry for mgmthost.  It didn't help.