Need help getting an Open NAT with a bridged connection.

Greetings!

Can you confirm that your Linksys WRT160Nv3 is up-to-date with the latest version of firmware. I suggest that you visit Linksys website, to make sure your router's firmware is up-to-date.

What is the make and model of your modem?

Do you have a third party firewall installed on your computer?

This should help you:
forums.xbox.com/.../370195.aspx

This will guide you through turning off your Firewall for your router. Unfortunately, there are limited settings to this router, so there are limited options on removing levels of security in order to allow Xbox traffic through.

I have taken the bridge off already. I am using the Hiro alone. When I used the Hiro bridged to the Linksys I was able to obtain an open NAT, but it slowed my connection down. Now that I have taken the bridge off I can't get an open NAT but my connection
is fine.

Great stuff

So are you using bridging or Internet Connection Sharing? ICS will normally give you a moderate NAT with that set-up but you should be able to get an Open NAT with bridging

Tem is partly right about the NAT problem, but it is actualy possible to get an open NAT with this type of connection. The trick is to use a 'bridged' connection rather than an ICS connection. ICS will always give your connection a strict or moderate NAT.
This guide explains how to use a Network bridge connection:

http://support.microsoft.com/kb/978618

I wouldn't have thought a moderate or strict NAT would cause issues downloading from LIVE, I could be wrong though.