I see this a lot with WEP and hidden SSIDs.

Your post does not reveal the router settings so here's the fast recap from the CNET Networking forum.

1. Router defaults then only what we need for the ISP.
2. A new simple SSID
3. WPA2 and AES for security.

Try that.

PS. Folk continue to lose time over "other machines work." That's discussed so let's move to the usual.