Having just upgraded to Ubuntu 8.10 my key observation is that it's important to read the release notes first.

http://www.ubuntu.com/getubuntu/releasenotes/810

There are a few bugs which have affected me

Three are definately putting a transparent proxy between me and the network.

I just got this error message

Network Error (tcp_error)

A communication error occurred: "Connection refused"
The Web Server may be down, too busy, or experiencing other problems preventing it from responding to requests. You may wish to try again at a later time.

For assistance, contact your network support team.

Which isn't coming from my web browser (which has a different error page for this problem).

And it isn't coming from the remote server as the message is that it couldn't connect!