ADC Clients are unable to access PDC client Via Netbios

Dear All
we have three servers one name
AA (PDC)
BB (ADC)
CC (DB SERVER),

db server(CC) server is at pdc(AA) site the adc (BB)is on vpn ..
Recently we have switched our db server to G8 server with the same machine name (SACSQLDB)
Now majority of my adc(BB) client are unable to access SACSQLDB e.g \\SACSQLDB
We can ping the namehost
We can ping with its ip address
We can also access this machine through its ip e.g \\172.16.2.10
We can ping and access from our adc but not from its clients
For test we added new machine (client) at PDC (AA) and my ADC clients are not able to access it too
Any clues