Kerberos/SPNego Negotiate not working correctly?

@Override
protected void parseChallenge(
        final CharArrayBuffer buffer,
        final int beginIndex, final int endIndex) throws MalformedChallengeException {
    final String challenge = buffer.substringTrimmed(beginIndex, endIndex);
    if (log.isDebugEnabled()) {
        log.debug("Received challenge '" + challenge + "' from the auth server");
    }
    if (state == State.UNINITIATED) {
        token = Base64.decodeBase64(challenge.getBytes());
        state = State.CHALLENGE_RECEIVED;
    } else {
        log.debug("Authentication already attempted");
        state = State.FAILED;
    }
}

@Override
protected void parseChallenge(
        final CharArrayBuffer buffer,
        final int beginIndex,
        final int endIndex) throws MalformedChallengeException {
    this.challenge = buffer.substringTrimmed(beginIndex, endIndex);

    if (this.challenge.isEmpty()) {
        if (clientCred != null) {
            dispose(); // run cleanup first before throwing an exception otherwise can leak OS resources
            if (continueNeeded) {
                throw new RuntimeException("Unexpected token");
            }
        }
    }
}