https://discussions.apple.com/docs/DOC-3421 Hopwefully you'll find the answer there, it sounds like it may have something to do with your Mac's wifi card
I have a MacBook Air that has no Ethernet ports. Is it possible to connect to the modem without the Ethernet cable? If so, how do I go about doing that?
(I tried looking up this answer in the forums but I’m locked out of it. It brings me to the homepage of the forum instead of the post. I apologize for the repost.)
If you are talking about a Gateway device the answer is yes, you can connect to it it via WiFi. If you need more advice, please post back.