I am running 11.10 on my PC. The Update Manager once indicated that I could upgrade to 12.04 LTS. However, clicking the upgrade button made the update manager unresponsive and I had to force quit the app. The next time I started the app, it showed me all the updates except for 12.04. Is there anyway I can upgrade to 12.04??
You can add the repositories of the 12.04 version in the /etc/apt/sources.list and with the help of apt-get or aptitude in a console window try to update it.