How to debug router connection to cable modem

I have a linksys WRT54G wireless router that was working fine for 4 days and then I lost connection to the internet.  If I plug the modem directly into the computer I get a connection.  When I plug the modem into the WAN connection of the router things get odd.  I can connect to the router without a problem but the connect between the router and the modem is lost.  I tried several different cables and a D-Link DI-624 router and got the same results.  

I have no clue where to start now.

Thanks for any help.
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Your Linksys should have a MAC address clone option. Enter your computer's MAC address there and select  * enabled
To find your PC's mac address, use "ipconfig/all" and look for the Physical address. Put that address into the LInksys. Save Settings.
Power off the cable modem
Power off the Linksys
Go get a beer - wait 10 minutes. Really.
Power up the linksys - wait 1 full minute
Power up the cable modem

You should be up and running in another 30 seconds to 1 minute..
Rob HutchinsonDesktop SupportCommented:
If you tried two different routers attaching your internet modem to the WAN port on each router with the same results, then there's likely something going on with the internet modem.

When you connect the cable from the internet modem to the WAN port on the router, are you power cycling (restarting) both the internet modem and the router?

When you have the routers attached, can you go into the web page setup for these routers and see if the WAN interface is setup for DHCP. If it is, what IP address are you getting? Compare this WAN interface IP to the IP that your computer is getting when you attach the internet modem directly to the computer.
Try factory resetting the device, install the latest firmware for that version of the device, and then set it up again for your network, complete with securing it if you are using WiFi.  If you can, make sure in the Status (or maybe it's called "Administration" for that model) is getting an IP from the modem.  If not, unplug your computer from the router and unplug the router and modem, wait 30 secs then power on the modem, then the router, then connect your laptop and see what happens.

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elentiniAuthor Commented:
This worked but I don't know why I have to keep doing it.
See if you can enable logging on your router - you shouldn't have to power cycle so often unless you have bad equipment (maybe try swapping out the router or modem with a temp one?) or if there is a setting that is somehow causing your computer (and the router) to look someplace else for data flow.
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