network port 445 question

Hello All,
I am running win2k/2k3 with xp clients.

Does 445 (microsoft-ds) port need to be open for clients accessing the
domain? I ran portqry on this port and it responds with it filtered. Also, I
read somewhere that client use port 1023 when making request for name
resoulution to DNS servers which use exclusively 53. I have several
different subnets here and am incurring numerous domain not found errors
(eventid 1054) from my workstations. Although, most say that this is a DNS
issue, The DNS is performing fine (netdiag/dcdiag) and it seems to occur
more often and randomly on machine located off the subnet where the servers
reside. I tried all aspects of troubleshooting from docs found on web but it
seems to me that there is a major infrastructure problem here. This is
extremely problematic particularly for implementing intellimirror scenarios
(eg such as GPO).

Any suggestions about the ports?
TIA<
Altria