U may have to change/lower your browser settings, it could be that simple, however, this is usually a firewall related issue.

Yep....agree with mechbas here!
If your connection has been established, but you cant recieve any web pages through your browser, then something within your own operating system is denying this.
If you are running windows firewall or another third party firewall, try disabling it, and see if you can access web sites then. If successful, you have found your problem. Dont forget that some antivirus software have their own firewall installed also (ie AVG pro) so you will need to check this out, depending on which program you are running.
You could also try rebooting your modem to see if this helps! (switch at the back)
It is then extremely important (from a security point of view) that you also re-enable your firewall after all this, and configure your access permissions within the software to allow future browsing!
Let us know if this helps!

Good Luck

Hey, I have the exact same problem. I moved and got comcast and it worked for a day or so but then stopped. My wifes laptop works fine, i called comcast and belkin and did trouble shooting with them and they said it is a firewall issue. I have turned my firewall off and i still cannot access , I am at a loss on what to do now.

open this window <start> <run> then type this command

cmd

now when you type this in tell me what it says.... ipconfig
hit enter
write down all the numbewrs and tell me what they say and i can help

Maybe a stupid question, but are you using WEP or WPA(2) encryption? and did you use the correct key to connect to the router? Often connectionproblems can occur when you use the wrong network-key.

i have treid all the above but still cant get me a solution.wat do i do next.

Zxor has it right:
Start, Run, CMD, OK to open a command prompt:
(For Vista or 7 type CMD in the Search box after Start)

Type the following command:

IPCONFIG /ALL

[Note that there is no space between the slash and ALL.]

Right click in the command window and choose Select All, then hit Enter. Paste the results here.

the key to after geting into the command prompt will tell you all about your connection
look at the host name if its your computer name on there then you not connected.. if the subnet is 255.255.0.0 then your not connected

I am having the same issue. I am on my laptop now through Sprint wireless, and am sitting next to my desktop that is connected through AT&T's internet service but I cannot get on all of a sudden. I am getting the 255.255.0.0 in ipconfig.
Help!