W:Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/karmic-updates/main/source/Sources.bz2 Hash Sum mismatch, E:Some index files failed to download, they have been ignored, or old ones used instead.
This is what I ended up with trying to upgrade to 9.10, and the whole process died because of one URL. In this case, it is complaining about an Australian server, since local ones are automatically added to your software sources list. But you can get yourself out of this by changing the server, at least for the upgrade, and choosing a safe bet like that in the U.S.
Go to System > Administration > Software Sources and in the first tab (“Ubuntu Software“) you’ll see what server you’re currently using next to Download from: -it will either say a custom server is being used, or that of your country (in the case of Aussies, it will say “Server for Australia“).
Simply choose “Server for United States“, let new software lists be downloaded and refreshed, then try again to upgrade Ubuntu via Update Manager. It should now work fine.