Two working decipher keys giving various, valid results for one ciphered message - is it possible?
This property can be achieved with a One-time pad.


  "In fact, it is possible to "decrypt" out of the ciphertext any message whatsoever with the same number of characters, simply by using a different key, and there is no information in the ciphertext that will allow Eve to choose among the various possible readings of the ciphertext."


This is nicely shown in this example from Wikipedia (section "Attempt at cryptanalysis").