The login failed when connecting to SQL Server DB-SERVER

RendyPrawira

Dear All,
i have a problem with sql server and navision 2009 r2.
my environment is like this :

trusted domain two active directory.
192.168.0.105 - AD-SVR - New Active Directory
192.168.0.104 - APP-SVR - Old Active Directory & Application Server(Navision 2009 R2) with Old Domain
192.168.0.103 - DB-SVR - Database Server. SQL Server 2008 with Old Domain

Service Account:
SQL Server : Old domain account -> navadmin
Navision : Old domain Account -> navadmin

when i try to connect RTC windows authentication from client computer with new domain, there is error "The login failed when connecting to SQL Server" but if i login with old domain, it is working.

it is happen almost everyday. after around 15 minutes, it can connect again. i don't know what happend.

how i can check the problem. it is problem with the trusted domain or the sql server or navision 2009 R2 ?
sorry if my english is bad.

thanks.