Okay, this might seem a little strange but are you launching the disk from the EvoX dashboard or are you rebooting?
The reason I ask is because I believe that EvoX network settings don't load until the dash loads, and is lost when the machine is powered off. This is where I think the problem lies. Because EvoX is setting up the network first, and then Halo is trying to use it but with settings that are different from Microsoft's pre-programmed addressing. Now what I'm going to guess is that when you come to trying the other hub, you leave the disk in and when you turn the box's on, they auto-boot Halo and thusly using Halo's network config.
I hope that makes sense, and I know it could be a little far fetched but I'm trying to go through everything I can think of!
Also, have you tried using the same hub, but with the PCs disconnected?