Troubleshhoting while upgrading UBUNTU 11.10

While trying to update to UBUNTU 11.10 I was getting following error:

W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/dapper/main/source/Sources

All I did I opened /etc/apt/sources.list and commented the following lines :

deb-src http://archive.ubuntu.com/ubuntu dapper main multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper-updates main multiverse
deb http://archive.canonical.com/ lucid partner
deb-src http://archive.canonical.com/ lucid partner

Then System >Administration >UpdateManager 

Click Upgrade.Follow the on-screen instructions.