When enabling DSE specific authenticaton in DSE 3.1, Java clients and c# can not connect.
Original Post: http://www.datastax.com/support-forums/topic/binary-protocol-with-internal-authentication-does-not-work-in-311-1
DSE 3.1 includes some security backports from v2 of the cql protocol, due to be included in Cassandra 2.0. These replace the authentication part of the protocol with a more robust & extensible SASL-based mechanism.
For this reason, DataStax has created DSE-specific versions of its open source java & c# drivers which support this authentication. The c# driver is still in beta, but the full source is available here: https://github.com/datastax/csharp-driver and the version which supports DSE 3.1 with authentication is found in this branch https://github.com/datastax/csharp-driver/tree/dse_3.1
You can find the appropriate Java driver at https://github.com/datastax/java-driver/tree/dse_3.1