If I connect an Apple 24" LED Cinema Display to a MacBook Air, it uses up the Air's one USB port. But there are three USB 2.0 ports on the back of the Display. So can I plug the USB to Ethernet adapter into the display and allow the Air to work on an ethernet network through the Display's USB port?
This might not be the most help since I don't have your display, but assuming that the display is functioning as a USB hub, you should be okay. I have a powered USB hub connected to my MacBook Air and the ethernet adapter works absolutely fine with it.