Removing PPA`s to proceed with update manager seems risky

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http://askubuntu.com – After failing to update 11.10, I found a non-working ppa source, which was some guys repository, containing software that I didn`t manually install. How do I know the consequences of deactivating this source and most likely, leaving this update at its current state for a long time? Why update manager just can`t forget about that ppa temporarily and try to update it next time? Is there a way to save my time and stop caring about OS internal components? (HowTos)