Laptop wont connect to internet via router

Hello,
I have a D-Link DI-524 router that we have been running a laptop off of. This router/signal was running fine for many months until just recently when it shows a signal but can't connect to the net. I have tried rebooting the router and changed the chanel etc..but it still doesn't respond. My son took the laptop to a friends place to make sure it wasn't his laptop and it worked perfectly. Any suggestions??

Thanks,
MC