When I was first trying to get my 360 to connect to my PC, I thought I was going to beat my brains in trying to figure it out. I'm running Windows OneCare as my firewall package. In that program (created by the same people who made the 360), there is an option to open ports for 360 traffic. Even after I enabled this setting, I was still unable to make a connection. After hours and hours of research, I finally found a website that was able to give me the settings that needed to be made. I'm going to post an instruction manual I made for myself way back when. You'll notice these are specific to OneCare, but at least you'll have the Port settings so may be able to make adjustments manually inside your firewall.
Windows Media Connect Software can’t get past the Windows OneCare Firewall unless you open ports manually.
Before Installing Windows Media Connect, be sure to open the ports or the software will not find the XBox on the network.
Here is how to open the ports:
1. Open Windows OneCare.
2. Click “View or change settings” on the left of the screen.
3. Click the “Firewall” tab.
4. Make sure the selection bar is set to the middle position, or “Auto (Recommended)”.
5. Click the “Advanced Settings” button.
6. Click the “Ports and Protocols” tab.
7. Click “Add”.
8. Name the first port “XBox 1”.
9. Choose “TCP” and make the port range 2869 and 2869.
10. The Scope is “Local Network” only.
11. Click “OK”.
12. In the same manner, open TCP Port 10243 and call it “XBox 2”.
13. The rest of the ports are UDP Ports, NOT TCP!!
14. Open ports 1900, 10280, 10281, 10282, 10283, 10284 and name them “XBox 3”, “XBox 4”, etc.
15. When you are done, close all OneCare opened windows.
16. Install the Windows Media Connect Software.
Make sure, if you are setting up IPs manually, that each box has a unique address.
To save on a monthly bill, you could nix the extra two IP addresses your ISP is providing you. Replace the HUB with a router and let it run DHCP. You could then have all other devices (PC and 360) pick up an IP from the router dynamically.
I know you are ruling out the Firewall Factor since your firewall was disabled, but make sure you don't accidentaly have any other firewalls installed and/or activated such as the Windows Firewall. The Windows Firewall blocks inbound traffic only. That means that WMC is able to ask the 360 if it would like to communicate, but your XBOX would not be able to respond.
One last note, the software should install even if you are unable to detect your 360 on the first go round. After the install, let the software run. The first time, it takes a while for it to kick off as it scans your HDs for media to share. After it's running, and assuming you get all your knotts untied, you'll see your 360 pop up in the device list of WMC as soon as you power it on. At that point, you'll simply click the 360 console in the device list and click "Allow".
I hope this is of some use to you. If it isn't we'll go back to the drawing board again.
Magus signing off......