Can't connect to internet through wireless connection

Have netgear rangemax router connected to dell dimension 46oo(windows XP). works fine, connects to internet. have a netgear PC card adapter on laptop, it connects to router and gets internet just fine. have a netgear rangemax next usb 2.0  adapter connected to new dell dimension E521 with Vista premium on it. It connects to router with a strong signal and also says I am connected to internet, BUT I can't get any pages to come up. Get the message the Explorer cannot display page because...

not connected to internet or typed adress wrong, etc... I get this no matter what page I try to view.

I have contacted netgear tech support. Everything is set right. they told me I had to turn off McAfee firewall or I can't connect. I did this-at least I think its turned off. I've turned off everything that has a McAfee name on it and rebooted and STILL NO INTERNET. Even though it says I am connected!

Any ideas on what is going on here? Do I need to turn off Windows firewall also? I have protection thru my ISP provider- Comcast- does that translate through the routers or is my computer going to be at risk by turning all the firewalls off? Do I also need to turn firewall off for main computer that is connected to router?

I've been trying to get this set up for days. Very frustrating!