Comment 4 for bug 224486

I think you're probably right about the archive. Looking through your console output you've done nothing obviously wrong. The only thing that comes to mind is that the guide you linked to is for upgrading from 6.06 rather than 7.10 and it uses the server upgrade method rather than desktop for Ubuntu rather than Kubuntu. As far as I know this should still work. For completeness sake it might be worth trying the instructions from the official upgrade guide which are here https://help.ubuntu.com/community/HardyUpgrades/Kubuntu.

Let us know how it turns out