BDC can’t validate

every time the PDC goes down, the bdc can’t validate users even if i try to open usrmgr.exe or srvmgr.exe shows a error “can’t access the domain”. the event viewer shows
1.- Redirector has timeout a request to domian
2.- the pipe is invalid
3.- NT LM security support provider service terminated with service-specific error 3056

the NDS4NT is loaded on the BDC and PDC (becouse there are in diferents locations)
When i try to logon on to the domain a got the error “domain can not be found”