I am trying to upgrade my 11.04 Ubuntu to a newer version. 11.04 has been by far the most stable and appreciable one so far for me, but I'd like to give my computer a little change.

However, when I go to Update Manager and click upgrade, it tells me I have network connection problems... meanwhile I am here writing this post on the internet, so I don't get it. The same occurs if I check for any kind of update. Anyone knows what is happening?

Oh and also, it says I have 11.04, but my upgrade option is to a new version of Ubuntu 11.04.... I don't get this as well. Why does it not propose 12.04 or 12.10 directly?

error details for UPDATE:
"W:GPG error: http://www.openprinting.org lsb3.2 Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7A4B44C2D2A2203E, W:Failed to fetch http://extras.ubuntu.com/ubuntu/dist...86/Packages.gz 404 Not Found
, E:Some index files failed to download, they have been ignored, or old ones used instead."

error details for UPGRADE:
"W:Failed to fetch http://extras.ubuntu.com/ubuntu/dist...86/Packages.gz 404 Not Found
, E:Some index files failed to download, they have been ignored, or old ones used instead."