As part of a troubleshooting exercise we uncovered what appears to be a not commonly known limitations in host names.
"Avoid using the underscore (_) character in machine names. Internet standards dictate that domain names conform to the host name requirements described in Internet Official Protocol Standards RFC 952 and RFC 1123. Domain names must contain only letters (upper or lower case) and digits. Domain names can also contain dash characters ( - ) as long as the dashes are not on the ends of the name. Underscore characters ( _ ) are not supported in the host name. If you have installed WebSphere Application Server on a machine with an underscore character in the machine name, access the machine with its IP address until you rename the machine."