[ubuntu] Cannot upgrade 10.04 and Stuck in 10.10

I made a mistake.

I tried to upgrade my Ubuntu from 10.04 LTS.
Then, I upgraded to 10.10.

It's really funny, then, the system tells me this is an unsupported version, and I cannot upgrade to another unsupported version target. :confused:

So, I think this is an issue for Ubuntu community.
10.04 is a LTS version, which should provide a way for the user to upgrade to 12.04 directly. Or at least, no wrong message for the user to upgrade to 10.10, and leave them there without a way to upgrade.

While I click 'upgrade' in 10.10, I got the following error message.

W:Failed to fetch http://extras.ubuntu.com/ubuntu/dist...64/Packages.gz 404 Not Found
, E:Some index files failed to download, they have been ignored, or old ones used instead.

Appreciated if anyone can help, how can I proceed to upgrade Ubuntu. :o