I had some problem with my Beaglebone rev A4 board. The network connection didn’t work at boot, but when i rebooted the system after booting into Linux, it worked…? pretty strange… So i made a google search and found http://circuitco.com who had more information about the issue. It seemed like a hardware issue, and the only way to solve the problem, was to remove resistor R219.
“We are looking into a SW workaround, but right now the easiest solution is to pop off R219 on the back side of the board under the RJ45 connector”

Check out http://youtu.be/Ak30G-shiYY to find out where the resistor is located and how to remove it.

After I made this modification my Beaglebone worked like a dream. So now im happy again 🙂