It means there's a DNS problem, like when sshd looks up the hostname
returned by the one resulting from a query on your IP, it doesn't get
your IP back.

i.e.
tentative_hostname <-- lookup(client_ip)
if (client_ip != lookup(tentative_hostname)) {
        // melodramatic warning message
}

-jeff

>
>> Anyone can tell me what this is about?... I get it when ssh'ing to my
>> server.
>>
>> reverse mapping checking getaddrinfo for pcts20.omrf.hsc.net.ou.edu
>> failed - POSSIBLE BREAKIN ATTEMPT!
>>
>> q
>
>