I’ve just finished upgrading my desktop and laptop system without any problem. By default Ubuntu 8.04 LTS will not offer a upgrade to 8.10. This is because the 8.04 LTS version is a long term support release and 8.10 is a regular release. However, you can do network upgrade by configuring LTS release to normal release as follows:
Click on System > Administration > Software Sources
Next click on the “Updates” tab and change “Show new distribution release” to “Normal releases”:
Click on Close to save the changes.
Ubuntu 8.10 Upgrade Over The Internet
Click on System > Administration > Update Manager:
Next click the Check button to check for new updates. If there are any updates to install, use the Install Updates button to install them, and press Check again after that is complete. Finally, a message will appear on screen, informing you of the availability of the new 8.10 release as follows:
Click on Upgrade button and just follow the on-screen instructions. The procedure may take some time.
A note about Ubuntu 8.10 server upgrade
Please see this article to perform network upgrade for Ubuntu servers.