Reason for "no Internet access"?

Hello,

My daughter's Dell laptop, which is running Windows 7, is no longer able to connect to the Internet. The wifi connection to our broadband router is established, but in Network and Sharing Center it says that there is no Internet access for this connection. I have also tried using an Ethernet cable, but this makes no difference.

Other connections on the network - two iPads, a desktop, my son's laptop, TV and Sky box - all continue to connect and work as normal. It seems that the problem must be with the Dell laptop settings, but I can't work out what. I've reviewed a number of forums and tried a few of the more obvious checks, but still have the problem.

Has anyone else had a similar proble/know of a solution and can help me out, please?