Now the bad news, the issue with two md5-sess examples in draft smith-sipping-auth-examples might be in fact precisely what RFC 2617 says, as reported in a semi-official erratum. If that's correct the md5-sess in RFC 2831 would be different. Hopefully draft melnikov-digest-to-historic will shed some light on this before it moves RFC 2831 to historic. For more about this see the IETF SASL WG mailing list.
For now the MD5 test suite still uses only the binary x2c(HA1) form instead of the hex. HA1 form in its md5-sess calculation.