"Server refused public-key signature despite accepting key" error generated when trying to import/create a 2048 bit DSA key pair.

Solution: To create a 2048 bit DSA host key pair for use in Cornerstone/Titan, use puttygen to generate the keys, export the public key in openssh format (and import it into Cornerston/Titan), and pull the private (.ppk) file into the client's key ring.