Problem: Can't upgrade from 11.10 to 12.04 LTS

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http://askubuntu.com – 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?? (HowTos)