Starting a week and half ago my router stopped working with my cable modem.  I went to sleep with it working and woke up with it not.  I swapped in another router and am still having issues; I was gone for 10 days so now I'm back to trying to figure it out.  While I was gone I left everything (cable modem, router, and computer) powered off.
My setup:
Comcast Ambit cable modem (from Comcast)
Netgear WGR614 v4 router  -- replaced with Linksys WRT54GS v1.1
Windows XP SP3
other computers, all currently unplugged
The modem is using the firmware (ver 2.105.2001) provided by Comcast; hardware version 1.3
The Linksys router is using FW ver 4.71.4 (latest for this release of HW), factory defaults
I am only using the wired connections; no wireless.
I have swapped out all of the cat5 cable.
If I plug my computer directly into the cable modem, I can ping by name or number.  Everything works perfectly.  
If I plug my computer into the router and the router into the modem, I cannot access anything outside of my local network.  This is the exact setup I've used for the past 5 years; there were no changes in the past year.
Now here's the interesting part:  I can log into the Linksys router and get status information from it; everything appears good.  Using the Diagnostics, I can run ping and traceroute to any site on the internet.  These work perfectly.  From my computer, I can ping the router and the modem.  However, I cannot ping anything on the internet by with name or number. If I plug in another computer, I can ping it successfully.
I've included two transcripts below that show these two attempts.  Addresses, DNS, gateways, etc. look good.  I cannot access the internet through either router.  
I am at a loss here.  Suggestions?  Help!
Computer to Router to Cable Modem
C:\ipconfig /renew
Windows IP Configuration
No operation can be performed on Bluetooth Network while it has its media disconnected.
Ethernet adapter Local Area Connection:
    Connection-specific DNS Suffix  . : hsd1.ca.comcast.net.
    IP Address. . . . . . . . . . . . : 192.168.1.100
    Subnet Mask . . . . . . . . . . . : 255.255.255.0
    Default Gateway . . . . . . . . . : 192.168.1.1
Ethernet adapter Bluetooth Network:
    Media State . . . . . . . . . . . : Media disconnected
C:\ipconfig /all
Windows IP Configuration
    Host Name . . . . . . . . . . . . : wynton
    Primary Dns Suffix  . . . . . . . :
    Node Type . . . . . . . . . . . . : Unknown
    IP Routing Enabled. . . . . . . . : No
    WINS Proxy Enabled. . . . . . . . : No
    DNS Suffix Search List. . . . . . : hsd1.ca.comcast.net.
Ethernet adapter Local Area Connection:
    Connection-specific DNS Suffix  . : hsd1.ca.comcast.net.
    Description . . . . . . . . . . . : Intel(R) 82562V-2 10/100 Network Connection
    Physical Address. . . . . . . . . : 00-1D-09-9B-45-EB
    Dhcp Enabled. . . . . . . . . . . : Yes
    Autoconfiguration Enabled . . . . : Yes
    IP Address. . . . . . . . . . . . : 192.168.1.100
    Subnet Mask . . . . . . . . . . . : 255.255.255.0
    Default Gateway . . . . . . . . . : 192.168.1.1
    DHCP Server . . . . . . . . . . . : 192.168.1.1
    DNS Servers . . . . . . . . . . . : 68.87.76.178
                                        68.87.78.130
    Lease Obtained. . . . . . . . . . : Monday, March 22, 2010 10:21:55 PM
    Lease Expires . . . . . . . . . . : Tuesday, March 23, 2010 10:21:55 PM
Ethernet adapter Bluetooth Network:
    Media State . . . . . . . . . . . : Media disconnected
    Description . . . . . . . . . . . : Bluetooth LAN Access Server Driver
    Physical Address. . . . . . . . . : 00-0A-3A-6F-68-41
C:\ping google.com
Ping request could not find host google.com. Please check the name and try again
.
C:\ping 74.125.19.104
Pinging 74.125.19.104 with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Ping statistics for 74.125.19.104:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
C:\
Computer to Cable Modem Directly
C:\ipconfig /renew
Windows IP Configuration
No operation can be performed on Bluetooth Network while it has its media disconnected.
Ethernet adapter Local Area Connection:
    Connection-specific DNS Suffix  . : hsd1.ca.comcast.net.
    IP Address. . . . . . . . . . . . : 71.204.149.195
    Subnet Mask . . . . . . . . . . . : 255.255.252.0
    Default Gateway . . . . . . . . . : 71.204.148.1
Ethernet adapter Bluetooth Network:
    Media State . . . . . . . . . . . : Media disconnected
C:\ipconfig /all
Windows IP Configuration
    Host Name . . . . . . . . . . . . : wynton
    Primary Dns Suffix  . . . . . . . :
    Node Type . . . . . . . . . . . . : Unknown
    IP Routing Enabled. . . . . . . . : No
    WINS Proxy Enabled. . . . . . . . : No
    DNS Suffix Search List. . . . . . : hsd1.ca.comcast.net.
Ethernet adapter Local Area Connection:
    Connection-specific DNS Suffix  . : hsd1.ca.comcast.net.
    Description . . . . . . . . . . . : Intel(R) 82562V-2 10/100 Network Connection
    Physical Address. . . . . . . . . : 00-1D-09-9B-45-EB
    Dhcp Enabled. . . . . . . . . . . : Yes
    Autoconfiguration Enabled . . . . : Yes
    IP Address. . . . . . . . . . . . : 71.204.149.195
    Subnet Mask . . . . . . . . . . . : 255.255.252.0
    Default Gateway . . . . . . . . . : 71.204.148.1
    DHCP Server . . . . . . . . . . . : 68.87.76.10
    DNS Servers . . . . . . . . . . . : 68.87.76.178
                                        68.87.78.130
    Lease Obtained. . . . . . . . . . : Monday, March 22, 2010 10:18:50 PM
    Lease Expires . . . . . . . . . . : Monday, March 22, 2010 11:12:31 PM
Ethernet adapter Bluetooth Network:
    Media State . . . . . . . . . . . : Media disconnected
    Description . . . . . . . . . . . : Bluetooth LAN Access Server Driver
    Physical Address. . . . . . . . . : 00-0A-3A-6F-68-41
C:\ping google.com
Pinging google.com [74.125.19.99] with 32 bytes of data:
Reply from 74.125.19.99: bytes=32 time=20ms TTL=55
Reply from 74.125.19.99: bytes=32 time=17ms TTL=55
Reply from 74.125.19.99: bytes=32 time=28ms TTL=55
Reply from 74.125.19.99: bytes=32 time=18ms TTL=55
Ping statistics for 74.125.19.99:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 17ms, Maximum = 28ms, Average = 20ms
C:\ping 74.125.19.104
Pinging 74.125.19.104 with 32 bytes of data:
Reply from 74.125.19.104: bytes=32 time=18ms TTL=55
Reply from 74.125.19.104: bytes=32 time=18ms TTL=55
Reply from 74.125.19.104: bytes=32 time=17ms TTL=55
Reply from 74.125.19.104: bytes=32 time=16ms TTL=55
Ping statistics for 74.125.19.104:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 16ms, Maximum = 18ms, Average = 17ms
C:\