ssh dies

[Robert Storey]

Dear All,

An interesting and disturbing problem recently appeared on our server
which is running FBSD 5.3. Rather suddenly, all users found themselves
locked out because ssh stopped working. We had to send an email to tech
support at our hosting service (Netsonic). They said this seems to be
happening frequently on many FreeBSD servers (something to do  with
reaching the limit of ssh connections). They didn't tell us how to solve
the problem, but they suggested rebooting, which should return the 
server under our control. We asked them to reboot and they did, problem
solved for now.

I'm wondering if anyone knows what is causing this, and if there is a
permanent solution? The server was running fine for four months without
issues - this just suddenly came out of the blue.

TIA,
Robert