Suddenly I can't get through on the net.

I was working quite happily when - hey presto - my wifi just stopped working.
I have a dual boot setup with XP so I tried with Windows but no joy. My wife's mashine, with the same set up, also failed, which seemd to point to the router as the problem. But it seemed normal with the lights all woring OK. Just didn't flicker any more.
I tried the usual stuff - rebooting, turning off the router for a minute, resetting it but still - nothing.
Don' know when I can reply as I'm using the local library which is a fair walk from home and computers not always available. But thanks for any help.
Maurice