Ack, this confounded thing continues to elude me.  Ta for the responses so far.

I have my main machine hooked up to a gigabit switch now.  Also connected to that is an ESXi server running one machine to act as a rendernode.  I have two laptops here, one which is configured to be part of a domain at work (i7 CPU) and one which is purely mine for home use (i3 CPU), which I would expect to work better on my home network.

My main PC resumes rendering, with network rendering on and network logging on.

Here's how each of them reacts.

The i7 work laptop starts loading the scene, calculates lighting and particles, and then stops doing anything.  Mem usage is still over 800k sometimes, sometimes when I do this it drops to 150kish for Carrara.  CPU is 0.

The i3 home laptop does as the i7 does and this one seems to almost work.  Only when this laptop is running a rendernode do I see four grey 'N' blocks appear on the frame being rendered on my main Carrara installation.  However, they never render.  The i3 CPU usage for Carrara is at 0% while RAM usage is stuc at about 882k.

The ESXi machine also loads the scene, calculates everything, and then behaves exactly like the i7 laptop.

I have three machines here more than capable of working with my my PC's Carrara renders and it seems none of em want to talk to eachother.  I have set all the Render Room settings manually to match their IP addresses and all ports are reflected in eachother (defaults left as they are at 5020, 5040 and 5060).

What can I try to fix this?  It's so frustrating when it should be so easy. :(

EDIT: oh, this may be useful, the network.log contents:
Start Rendering:
 IP Address: 192.168.1.11
 Subnet Mask: 255.255.255.0
Broadcast to: 192.168.1.255
Registering Render Node: Ainge (192.168.1.12) 4 CPUs
Registering Render Node: bignode (192.168.1.7) 2 CPUs
Total Nodes: 0
Total CPUs: 6

I notice Total Nodes is 0, even after detecting the other two... is this expected?