Can't "see" network on some computers

[Toonda]

I have an Apple Airport network and it was working fine untill a few weeks ago, at which point two computers on the wireless network in my home (an Acer laptop and a Dell laptop) lost the ability to "see" the network, and therefore, to connect.

The laptops both have working hardware and can see other networks when taken out of the house, but they cannot see my home network. The network is WEP secured and, as I said, was working perfectly until a few weeks ago.

Is there some major driver update that the laptops failed to download? What would be the best way to get the computers back up and running ASAP?

Thanks for the help in advance!