[Networker] How to understand this 7.4 behavior on multihomed Windows

A Windows Server 2k3 R2 with Networker 7.4 backup client has two nics, is 
behind a firewall device, and uses IPsec to filter all traffic to a strict 
allows list.  
Nic 1 has DNS name A and allows all needed traffic with the backup server and 
domain controllers.  Nic 2 has a DNS name B not known to the W2k3R2 server 
(unless it decided to look up the PTR DNS RR) and this nic only allows a couple 
specific tcp ports (common services, not ports used by Legato) and only with 
specific machines not including the backup server. 
Backup has been successfully running for many months.  
Last weekend the save set email report had lines of form:
* DNS name A: C:\ 12345 save: SYSTEM error: client 'DNS name B' is not properly 
configured on the Sun StorEdge(tm) Enterprise Backup Server'
The day before the backup worked, and no one was working on machines over the 
weekend.
How does this happen?  Or more to the point how does one prevent it?
The server does not know the DNS name B, and it cannot communicate with the 
backup server on the IP associated with name B.
This happened once before and apparently corrected itself after two days. This 
time, stopping/starting nsexecd, cleaning out temp files, did not force a 
resolution.  However, the first backup after rebooting the W2k3R2 client was 
successful.
The only thing that seems plausible here is that the client is sending a 
response to the server (on IP of name A) that states the IP of name B (or 
perhaps the client did a DNS PTR lookup and sent the name).
Why in the world would it do that?
I have reviewed what I can locate, here, via Google, etc. and find issues that 
are close but not a match in this multihomes situation.  Adding the DNS name B 
at the backup server seems wrong as that IP cannot support the backup 
communication.
So, question is, how can one prevent this from reoccurring?
TIA,
Roger

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