My wife and I have AT&T U-Verse 18 Mbps service, and we regularly get speeds ranging from high 15 Mbps to high 18 Mbps. Until recently, that is. I noticed that the connection was sluggish. Usually I'd chalk it up to streaming HD via Netflix or Hulu, but then I started noticing that basic websites would load at extremely slow speeds when I'd be the only one on the network.
I did the usual trouble shooting steps: restarted the U-Verse gateway & the D-Link router, restarted the computer, etc., etc., but nothing fixed the problem. So I called AT&T. They did some basic over the phone trouble shooting (reset the gateway) which didn't fix the problem, and scheduled a tech for the next day.
The tech came out and started doing his trouble shooting. When he'd plug his laptop into the gateway, he'd get great speed. When I connected the MacBook directly to the gateway, I'd get less than 1 Mpbs down. If I connected the iMac or Mac Mini directly, I'd get 17+ Mbps down. If I disconnected the MacBook completely from the network, speeds would be great, even when doing simultaneous speed tests on 3 devices. If it was connected, whether via WiFi or ethernet, all devices on the network would get slow speeds. We thus determined the problem has something to do with the network card on the MacBook.
Since then, I've disconnected the ethernet connection from the MacBook, and only connect via WiFi when I absolutely have to do something on the MacBook. But it's a PITA to have to do that. I'm guessing that the network card is bad, and should probably be replaced. I have an appointment with the Genius Bar at one of the local Apple Stores for Sunday afternoon to have them trouble shoot it, but was hoping someone here could possibly shed some light on what might be the problem, and if there's a simple fix for it.
If it does turn out to be the network card (which is most likely part of the motherboard and therefore expensive to repair), would I be able to pick up a USB WiFi adapter for it instead, and have it connect via that? Or would the MacBook still use its own network system even if it's using a USB adapter?
I'm running OS X 10.6.8. It's fully up to date as of 6/24.
tl:dr - MacBook is slowing entire network speeds when it's connected either via WiFi or Ethernet. Network speeds are great when it's not connected. Speeds for all connected devices are slowed by the MacBook being connected.