Let's dig a bit deeper ...
> It is on a Ubuntu 9.04 os. it runs prfectly when accessed by the local address.
I presume you mean Ubuntu 10.04 (that's the only version that we test with the packaging of 0.80).
Is your Moodle server located on the same network as your BigBlueButton server? Specifically, can your Moodle server access your BigBlueButton server via HTTP requests.
The BigBlueButtonBN plugin must make direct API calls (via HTTP requests) to the BigBlueButton 0.80 server to create rooms, get recordings, etc.
For a BigBlueButton server on a local network (behind a firewall), when you access it with your browser (also running on a computer behind the firewall) everything works. However, if your Moodle server is located outside your network-- outside your firewall -- such as on a shared hosting site the external Moodle server can't reach in through your firewall to access your BigBlueButton server. The firewall is doing its job.
Let us know the networking setup of your BigBlueButton server and Moodle server and we'll dig a bit deeper.