Possibly OT: pgp key problem

Hello all, This is possibly (probably?) not TDE related, but I hope someone understanding more about the matter on this list can help: I've decided to upgrade TDE to R14 on y laptop runing wheezy. Everything went fine and I did not upgrade Debian (I did update, however). I get a message that no public key is available for two key IDs - I'm not 100% sure it was not allready so before the upgrade. When I try to import these keys I get the answer that the key was not changed (so the error remains). So I've got two questions that "googling" could not answer: a) how could I get an information about what repositories these missing/wrong keys are associated with? b) what happens if I simply ignore this sort of message (apart from the fact that some sources are not fully secure)? Thierry