Server response: No properly formed ip addresses

The other day I was looking into a problem on one of our hosting servers running Parallels Plesk 8.6. The server's license had just entered his grace period and retrieving the key resulted an error message as "Server response: No properly formed ip addresses" which seemed very odd! At first I thought maybe its a firewall issue but I was wrong. For me restarting the httpsd service resolved the issue (/usr/local/psa/admin/bin/httpsdctl restart) but I couldn't find out the root cause.