I get the same problem running ddclient 3.6.3. I tried a bit or troubleshooting but this looks fine:
[root@hosebag root]# ddclient -daemon=0 -debug -verbose -noquiet
cashe(...
...
cache{hosebag.kicks-ass.net}{wtime} : 0
CONNECT: checkip.dyndns.org
CONNECTED:
SENDING: GET / HTTP/1.0
SENDING: Host: checkip.dyndns.org
SENDING: User-Agent: ddclient/3.6.3
SENDING: Connection: close
SENDING:
RECEIVE: HTTP/1.1 200 OK
RECEIVE: Content-Type: text/html
RECEIVE: Server: DynDNS-CheckIP/0.1
RECEIVE: Connection: close
RECEIVE: Cache-Control: no-cache
RECEIVE: Pragma: no-cache
RECEIVE: Content-Length: 106
RECEIVE:
RECEIVE: <html><head><title>Current IP Check</title></head><body>Current IP Address: 24.12.133.135</body></html>
DEBUG: get_ip: using web,
http://checkip.dyndns.org/ reports 24.12.133.135
SUCCESS: hosebag.kicks-ass.net: skipped: IP address was already set to 24.12.133.135.
Always-on connection.
greg