Setting up trusts

Given the IP addresses, it looks like a routing problem. Does the router forward the ports [I'm forgetting exactly which ones] 135 through 139? [I think it's in that range.]

This is very common, when the different domains are on different network segments.
Do you do the 10.x.x.x address space under a Class C arrangement, with a 24-bit subnet mask (255.255.255.0)? If so, then I am not surprised that DomainA can talk to DomainC, but not to DomainB.
A and C are both on 10.0.1.0/24 (again, assuming Class C) and Windown works in this way best on the same subnet. It does not cross subnets well. You need to force it to do this.
Now, you can set up WINS servers on each PDC, link the WINS servers together (as push/pull replication partners), and that is SUPPOSED to work. But, in my experience, it doesn't.
The best way to set this up, where domains cross subnets and they can find the Domain Controllers in each domain, is to use the LMHOSTS file on each Domain Controller.
And here is a Technet article that tells you what to do and why:
http://support.microsoft.com/?kbid=180094

hope this helps

Can you give us more details? For example - why you use PDC notation - is it about NT domains? What is the relation between the domains: parent-child, root domains in the same forest, or else? Have you thought about using nontransitive trusts between domain A and B or C and B?

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