Ahh that's a whole horse of a different color...
Have you checked the settings for encryption, pass phrase and network name?
It's pretty obvious but that's where to start.
By any chance was the router powered down and back up over the weekend?
It's possible it may have lost settings in a dirty shutdown. Maybe you should re-check it's wireless settings as well.
Can you access the net if you go with a network cable on the router... at least that would tell you if it's just the wireless or the whole setup.
One of the early steps might be to power cycle the Router... unplug, have a coffee, plug it back in and try again.