我的8.04不能升级到8.10

[daniel]

网络升级，alternate 光盘升级都尝试了。出现下面的问题，请各位帮我解决！

W:GPG error: http://security.ubuntu.com intrepid-security Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5, W:GPG error: http://archive.ubuntu.com intrepid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5, W:GPG error: http://mirror.lupaworld.com intrepid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5, W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/ ... ackages.gz 302 Found [IP: 91.189.88.46 80]
, W:Failed to fetch http://mirror.lupaworld.com/ubuntu/arch ... ackages.gz 302 Found
, W:Failed to fetch http://mirror.lupaworld.com/ubuntu/arch ... Sources.gz 302 Found
, E:Some index files failed to download, they have been ignored, or old ones used instead.