Toshiba Satellite could not browse via Wi-Fi

Hello techy people!
I am having problems connecting with wireless networks.
I have a Toshiba Satellite laptop with Cisco Aironet 350 Wireless LAN Adapter installed on it. When I am at the office, I am using a VPN dialer in accessing the wireless network. But when I'm at home, I was unable to connect to any networks.
My computer can successfully detects the entire wireless networks available. In fact, my signal strength is good. But I cannot browse or open any sites on my laptop. My friends used to come over during weekends and they can very well access the internet without problems.
What is causing this?
Is there something that I need to set correctly such as cookies or anything?
Please help.
