Hi!
If you are using separete WINS server for each domain, yhen you must establish replication of WINS-database between them.
In WINS manager on both servers you must to configure each server as push and pull partner for another one. Besides in TCP/IP protocol configuration on these servers you need to set primary WINS on itself and secondary WINS on its replication partner
Example :
WINS1-192.168.1.1
WINS2-192.168.2.1
on WINS 1
primary WINS 192.168.1.1
secondary WINS 192.168.2.1
on WINS 2
primary WINS 192.168.2.1
secondary WINS 192.168.1.1
Sorry for my pure english.