Eu notei isso nos registros de sistema dos meus clientes:
5/14/11 11:00:51 PM SecurityAgent[2735] User info context values set for testuser
5/14/11 11:01:12 PM authorizationhost[2734] k5_authenticate(): got -1765328228 (Cannot contact any KDC for requested realm) on /SourceCache/SecurityAgent/SecurityAgent-39574/plugins/krb5/krb5_operations.c:84
5/14/11 11:01:12 PM authorizationhost[2734] -[SFBuiltinAuthenticate performDSPasswordAuth](): got -1765328228 (Cannot contact any KDC for requested realm) on /SourceCache/SecurityAgent/SecurityAgent-39574/authhostbuiltins.m:1039
5/14/11 11:01:13 PM SecurityAgent[2735] Login Window Showing Progress
O KDC está sendo executado no servidor, mas as portas do firewall foram bloqueadas. Eu desbloqueei as portas KDC (TCP / UDP 88), indo para o Server Admin > Firewall > Configurações > Serviços > Permitir: Kerberos V5 KDC
e agora o login na rede leva apenas de 5 a 10 segundos, o mesmo que nas contas locais.