I also had all kinds of trouble maintaining a connection with the USB. I tried two USB wifi devices. The recommended edimax nano and one that I purchased on Ebay with a larger antenna. The one with the larger antenna had a problem with the power plug getting in the way but was able to get it plugged in. Neither worked reliably. I tried two beaglebone black boards (I use them at work so I had several at my disposal for testing). I could get it to connect once in a while but would not hold up a connection. I did not do the above mentioned fix…. found this after I found the solution below.
Finally I purchased a tp-link TL-WR702N. Running this mini router in client mode I was able to and plugging into the rj-45 ethernet port on the bbb I have had absolutely not trouble. It has worked after every reboot and has not stopped once. This device is small enough to fit in the recommended enclosure with a OSBo, one 16 station expansion board and the plug in style transformer. It is a tight fit and requires too many extra cables, but it is working.
I am running my OSBo outside, in the weather proof en-closure. I am interested to see how it holds up to the Phoenix summers. It is 99 degrees right now and it is still running 🙂 We will see what happens when the temp gets up to 115.
-Mark