I am using ubuntu 10.10 currently and I was trying to upgrade to higher version but the update manager is not showing option for that. I also tried it using the terminal (sudo apt-get upgrade) and it is not working.

Also earlier I was having problem with some PPA to update the system before upgrading it.
It was related to the following PPA and I unchecked it from the Software Sources

But now there is no option of upgrading and from terminal also it is not working.

Please help me in upgrading to higher versions.

Thank you