Wireless connection

First I will confirm what you've posted.

Before going to your friends house you used to connect the laptop up via the network cable. Since youve tried your laptop on your friends wireless it no longer allows you to surf the web via the wireless nore the wired connection?

To me it sounds like a possible mis-configuration between your laptop and your linksys router. Depending on what operating system you are using you need to get into your network connection settings (usually in control panel) and either set the TCP/IP to automatically obtain ip address or set it correctly.

If you have never had to configure this in the past ensure that obtain automatically is set.