inbound ssh ceased on 4 servers at same time

[John Brooks]

Yesterday at about noon, all four freebsd servers on a clients lan
quit accepting ssh connections. All were running 4.11-release-p4,
and had been cvsup'd at the same time from cvs-10, cvs-11, or
cvs-12. Outbound ssh (from console of the affected boxes) works as 
expected, both to local openbsd boxes and to remote locations. 
There are no host based firewalls involved, and all other network 
services are operating correctly. Netstat shows port 22 as listening. 
At 11:20 am (40 minutes earlier), ssh was working properly on all boxes.

Has anybody encountered a situation like this before? 

--
John Brooks
john at day-light.com