Dynex router won't communicate with the modem.

what is the ip address of the cable modem ?
when connected directly to the modem can you do ipconfig in dos command window and find out the gateway ip address listed.
This has to be the gateway ip address in the wi fi router.
turn of DCHP server in the WI FI router and make its ip address one more than the cable modem ip address.
make sure subnet mask is the same in both devices
Make sure DHCP server in Modem has leases above 20 to allow other devices to use 1 - 19 .
eg 10.0.0.1 or 192.168.0.1 for cable modem ip address internally.
make wi fi router 10.0.0.2 or 192.168.0.2 depends on the ip address of modem ?
Gateway address of 10.0.0.1 or 192.168.0.1 depends on the ip address of modem ?
dhcp server leases from 10.0.0.21 to 10.0.0.254 depends on ip address of modem ?

The modem has likely assigned it's IP address to the MAC address of the PC.
We need it to assign an IP address to the WAN port MAC address of the router!
When you hook up the router, the modem is no longer sending data to the correct MAC address.
Unplug the power to both the modem and the router.
Power up the router FIRST, and wait for it to complete it's initialization.
Once the lights have settled down on the router, power up the modem.
Wait for it to fully initialize.
NOW turn on your PC or laptop, and everything should be working just fine.
If not, post a reply or add a comment to this post, and I will try to further assist you.

You mentioned in your question that you had a router. If it is actually a modem, then yes, you need a router.
The reason that the Ethernet hub is not working is that your modem will only give out 1 IP address to one device on the hub. With a router, the router uses the 1 IP address and shares access to the internet via that 1 IP address.
Yes, you'll need a router instead of a hub.

Modem <--> Dynex <--> your computer should work.

Connect:

Modem <--> Dynex <--> Linksys router <--> your computer.

Turn off all the above devices.
Turn the modem on, and wait for its lights to "settle" down to a repeatable pattern.
Turn the Dynex on, and wait for its lights to "settle" down to a repeatable pattern.
Turn the Linksys on, and wait for its lights to "settle" down to a repeatable pattern.
Turn your computer on, and wait for its lights to "settle" down to a repeatable pattern.

On your computer, click Start
Click Run
Type CMD and press ENTER
Type IPCONFIG and press ENTER
The Linksys router should have given you an IP-address for your computer, and the IP-address for the "gateway" (namely the Linksys router).
Start your web-browser.
Type http://192.168.0.1 (or http://192.168.1.1) to connect to the web-interface "inside" the router.
Access the 'WAN' settings-page on the router, to see what IP-address the Dynex router has given to the Linksys router, and what "gateway" IP-address that the Dynex router has offered to the Linksys router.

It might be best to change the range of "dynamic" IP-addresses that one of the routers hands out, e.g., '192.168.123.100' to '192.168.123.200' for the Dynex router, so that both routers don't try to hand-out IP-addresses in the *SAME* range.

so that means if you connect the computer to the modem, it works but not with the router.
it seems that the router and the modem are not communicating with each other.
When you connect the computer to the modem , check the IP address through the modem. If ti is private IP address then you will need to change the settigns on the router.
Click Here for more info about networking

Checklist:
* Is DHCP configured correctly?
* Connect your server and laptop to a switch (not directly with the cable)
* Can they ping each other?
* Check that the firewall is configured (or switched off if you have another FW in place)
* Default gateway should be your router, not the computers (until you have configured RRAS for example)

Here you can find more information about how to configure various roles in 2008: http://technet.microsoft.com/en-us/windowsserver/2008/default.aspx

Here is a link to their Support site: http://support.xbox.com/support/en/us/nxe/default.aspx Select "Troubleshooting/Connection" errors page. On the LEFT, select "Network Help". That should put you in the area you need.

I am not familiar with that router so I will provide general knowledge and you can apply it to fix your problem.
It sounds like your cable modem is willing to supply a single IP address. This can and should be connected to the WAN port of your router. The problem is that the router is not assigning IP addresses to the equipment that is connected to its LAN ports. Instead, it allows that single cable modem IP to be assigned to connection #1 and everybody else gets nothing. Get the computer working through it, connect to the router as per the owners manual and turn on NAT or DHCP, whichever it offers. Reboot the computer and connect xbox and you should be good. This was probably not an issue with DSL because your DSL modem would supply up to about 10 IP addresses and they also passed through the router.

Have your router clone the MAC Address of your computer. The MAC address is a hardware address on your network card and DSL providers seem to like to bind it to account. What is probably happening is when the router connects to your ISP and asks for an IP address, it looks up your account info and and decides - nope, wrong device. Cloning the MAC address will make them happy. If you are not able to clone the address, call your provider's tech support and ask them to clear the MAC address from your account. Make sure you have the router plugged into the modem and not the computer or you are back to where you started.

First whether the connection is pinging or not if pinging means its working may be the ip address problem