The default value for the checksum type should be RSA_MD5 , not RSA-MD5-DES.

RFC1510 mandates RSA-MD5_DES as a checksum type; howevere W2K does not support it; also both MIT and SEAM implementation set the default value to be RSA-MD5. So we should also set it to RSA-MD5 for the sake of interoperability. ( We could always ask users to set the checksum type to be RSA-MD5 in the configuration file but that will cause incovenience to the users)

Also when krb5.conf file is not available or not readable the error message should be more specific instead of throwing a Null realm exception.