This message may appear when the keys for SSH are generated and loaded for the very first time. It is a timing issue with respect to loading of the newly generated keys for SSH.
Issue the setup ssh show command in the PacketShaper CLI and look at the output. If the keys for RSA1 are not displayed, issue a setup ssh keygen command. This will generate keys for both SSH v1 (RSA1) and v2 (RSA and DSA) and the error message will go away.
For more information about SSH, see Modify SSH Settings in PacketGuide.