Wireless Laptop cannot connect to new router

Hi,

I got a Dell Studio Laptop running on Windows 7. It was able to connect to the router back home but will not pick up a connection with a new one in France. The Router is available and working on my flatmates laptop but when I type in the security key, it says that the connection cannot be established, that counts for all available Networks. I reset the router several times and rebooted my laptop but still is not working. Can anyone help me? The chat with the technical support is offline and I need a quick answer.