Get users error - LDAP

I have configured MD AD Directory in Crowd. And sometimes (i can't understand what does it depend on) i gat an error:

2009-08-24 18:03:00,398 http-8095-Processor24 ERROR [codehaus.xfire.handler.DefaultFaultHandler] Fault occurred!
org.springframework.ldap.PartialResultException: nested exception is javax.naming.PartialResultException [Root exception is javax.naming.CommunicationException: simple bind failed: **.*:389 [Root exception is java.net.SocketException: Connection reset by peer: socket write error]]

This error i get in Crowd, when i try to get list of users for this directory, for example, and i get this error in Confluence, when users try to login (error i can see in log file and users just get Ivalid login or password message).