A repository changed its public key?

One of the repositories checked during the online update I just tried to make seems to disagree with the signature/key I had actually registered it with:

http://tinyurl.com/2ovgnj

This is probably just paranoia, but I'm not so sure if I should press the "Trust and Import the Key" button :P I thought the plan is that those keys are not to change; if they do, it should mean that some sort of security compromise occurred.

Anyone else got the same?
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