konmatz
You shouldn't have to spoof the MAC address of your attwifi... in fact, I didn't even think that was possible...
Try to revert the changes. I don't recommend doing that, as it slows things down, and I believe there are workarounds. What's your OS?
Also, don't leave two 3DSs to connect in succession. My boyfriend and I left both of our 3DSs to connect, and strange things started to happen... He got the first StreetPass hit, then I got a StreetPass hit
from him shortly after--AND it hadn't even been the full 8 hours since we had a normal StreetPass. Next thing we realized, we were only simultaneously StreetPassing each other half the time. I fiddled with my Wi-Fi adapter's MAC address to try to get it to stop.... didn't change a thing. So I ended up having him disconnect from my 'attwifi' point, changed my wireless connection to a wired connection, and now it actually seems to be consistently working, leaving only 2 minutes (120 seconds) in between MAC changes!
Edit: It's tooootally working with the wired connection. Sooooo many streetpasses.
My recommendations for you... I could be wrong, but try this... (and try to get this to work
without spoofing a MAC over your attwifi)
*Uninstall and reinstall your USB Wi-Fi driver. If that still doesn't work for you, try out a few different USB Wi-Fi dongles, if you can.
*Make sure your internet connection isn't too fussy... Just make sure you have a good connection that doesn't break. That's why it's recommended that you use a wired LAN connection. It's still possible to have terrible internet with a wired connection, though.
Just make sure it can connect fine and that your connection isn't going out on you randomly.
*If you don't already have it, download and install Virtual Router. If you have the GUI pulled up, you should at least be able to see your 3DS connecting to your access point. You can see its IP, and if I'm not mistaken, its StreetPass MAC (which changes). If you see it connecting on the Virtual Router user interface, that's a good sign. Some MACs might not give you StreetPass hits. Don't sweat it! Just continue to cycle through them.