This gets new owners everyday. The wifi router may not have the latest firmware, even when new.
Bob
On Saturday, I had Comcast High Speed Internet installed in my apartment. The modem I was given is a Motorola SURFboard SB5120 Series, connected to my system via Ethernet. A few hours after the installation, I headed out to Best Buy and purchased the Linksys Wireless-G Broadband Router, Model No. WRT54GP2A-AT. This went with this router specifically for its VoIP capabilities with AT&T CallVantage. After a weekend of tinkering, I've yet to be able to get it working.
When my Cable Modem is connected to my computer, everything works fine, but when I add the router to the mix, I can not access the internet. Initially I went through the Linksys Quick Installation Guide, step by step, power cycle to power cycle to get it going, but when I was finished and it was suppose to work, I would get the same T pPage cannot be displayed' message in IE every time.
Thinking I may have missed something in the process, I reset the router to its factory defaults, and tried to run the Setup Wizard provided by Linksys on CD. I get towards the end every time, and then I receive an error message that the router is not able to connect to the internet, please turn the modem on/off, etc.
I tried to setup the router manually, but my network administration abilities are a bit lacking. Everything I found online seemed to indicate that for Comcast, use the 'Automatic Configuration (DHCP)', then Clone the MAC Address, and I would be good to go, but I've had no such luck.
When the modem is connected to the router, and the router is connected to the computer: the Power LED, WAN LED, and Ethernet Port LED are all lit and constant. The Internet LED, however, is flashing, as is the PC/Activity LED on the modem itself.
Here is my IP Configuration when the modem is connected directly to the computer:
http://www.astuder.com/temp/prompt_01.gif
Here is my IP Configuration after initializing the router setup:
http://www.astuder.com/temp/prompt_02.gif
Here is the Router Status:
http://www.astuder.com/temp/router_status.gif
Is there something I'm overlooking? Is this kind of configuration even possible with Comcast? I've stumbled across a few threads on different forums from last year with people having the same problems, but I was not able to get it working. I've read through both of the documents from Linksys below, but again I was unsuccessful.
http://linksys.custhelp.com/cgi-bin/linksys.cfg/php/enduser/std_adp.php?p_faqid=1040&p_created=1086911813&p_sid=uGENlxqh&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MiZwX3NlYXJjaF90eXBlPXNlYXJjaF9ubCZwX3Byb2RfbHZsMT0mcF9wcm9kX2x2bDI9JnBfc2NmX2xhbmc9MSZwX3BhZ2U9MSZwX3NlYXJjaF90ZXh0PWNvbWNhc3Q*&p_li=
http://linksys.custhelp.com/cgi-bin/linksys.cfg/php/enduser/std_adp.php?p_faqid=199&p_created=1084206387&p_sid=uGENlxqh&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MiZwX3NlYXJjaF90eXBlPXNlYXJjaF9ubCZwX3Byb2RfbHZsMT0mcF9wcm9kX2x2bDI9JnBfc2NmX2xhbmc9MSZwX3BhZ2U9MSZwX3NlYXJjaF90ZXh0PWNvbWNhc3Q*&p_li=
I will be extremely grateful to anyone who can point me in the right direction... thank you.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic