NO_PUBKEY error when checking for updates

I fired up Update Manager and I checked for updates and I get this error:

http://i.imgur.com/e5g4S.png

and I tried

Code:

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sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 531EE72F4C9D234C

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but this gave me THESE errors:

http://i.imgur.com/Ppps0.png

and I have no idea how to fix this. I assume the second error is because of my internet connection, but that's an assumption. I think I should try again later and by running the code above I should get this error sorted out right?

I know this is not thing you are looking for,but maybe to remove that ppa from source list and try to add it again with key.Just suggestion.