Opera 9 has a strict security behavior dealing with cross-frame scripting if one of the involved hosts is a "fake" host (i.e.: its name is set in the local machine hosts file and not in any DNS).

Usually such configuration is used to test a dual-server deployment using one single machine.

"Unfortunately" opera recognizes that a host name is read from the hosts file and denies any communication between such frames, blocking lightstreamer streaming.

By the way, note that such situation with Opera can only be experienced when using a single server (reached with two different host names to fetch pages and to get the streaming) because using two servers on the same machine will imply the port issue.