sqwint

Hi Guys
not sure of correct terminology for this problem but here goes. For two days I have had a new laptop and set up a wireless connection with a 3com router modem, and BT broadband. It worked fine until yesterday, and will now no longer connect to the web. It says it has a good connection to the network, but wont connect and the modem ip address settings show that the internet is not connected. Also the internet light is not on the modem.
The only thing that has changed was that I removed the Norton antivirus that also had web protection on it, as it was a free trial and I prefer another protector. It said it would put the windows firewall back to default, and I have not been able to connect since. Also I have connected to another wirless connection, and again get a good connection but no traffic to the web.
I am hoping someone can point me in the right direction of which settings to tweak to get the machine talking again!
Many thanks
Sqwint