Hello all,
Yesterday morning all was fine—I was able to log onto the internet as usual on our home wireless connection.

But then last night (at home) I couldn't log on. When I try, I get the Address Not Found box. (Nothing had changed: No one had used the machine and nothing about our home network had changed. All of the other computers—PCs—in the house are connecting fine.)

It seems to work fine on other WiFi networks.

Need more info please.
Laptop, PC?
Have you made sure the wireless is enabled? Its a common problem.
Has it been connected antwhere else since, like a work network?