LDAP Server is down

Hi,

I have established a trust relationship between two domain and I thought it was fine because I can see the users from each one of the domains but I needed to run this command:

setspn -l firsdomain\admin  

from the seconddomain and I get the error:

Ldap Error (0x51 -- Server down): ldap_open

Can anybody help me?

Which tests I can do to fix the problem?

Thanks in advance.

Regards.