Laptop doesn't want to connect to the network?

OK, my laptop won't connect to the wireless network. It says it's connected but won't transfer any data. It was working fine for over a year, but has stopped. I even tried turning off the firewall for a second to see if that was the problem, but nothing. I also tried plugging the network cable from my router in it (the same cable I normally use for my desktop), but I still had the same problem - it said it was connected, but it still wouldn't work (couldn't get anything to come up in a browser.) Later, when I plugged the cable in again, it said that wasn't even connected (and the LED by the network connection was orange.)

Any ideas what could be wrong, what I should check?

It is a Dell Inspiron 700m, running Windows XP, with Norton 360. The "Dell Wireless WLAN Card Utility" to manage the wireless connection. "Work Offline" is not checked and the correct wireless network is selected.

Everything looks "right", but no juice.