The company has three domains，Has set up a domain trust，Previously unable to add a user happens too，Later identified as a firewall to block 389 port of relationship。This time from a new Server，It occurs when setting directory permissions，Sometimes a user can add a trusted domain，Sometimes the situation can not find。
Internet search for relevant information on the，DNS suspected cause，Because there is this new Server from AD，There DNS service，But when I set，Only into their domain DNS settings，No other trusted domains，After the DNS information into other domains is also located，Sure enough resolve this issue。
[Links]
- Windows 2008 Trust website
- Old Sen Chang Tan » Security settings can not add users
