For no apparant reason, when I plug my Macbook Air into my Thunderbolt display, the ethernet plugged into the display is not recognized. If I do a reboot, it comes back to normal. I don't recall any changes I would have made, I just started to notice that the ethernet would not be connected or available, and I would be on WiFi instead. At the same time, sometimes the USB keyboard is not recognized either. I will have to unplug it, and plug it back in. This is all fairly recent, for weeks the display worked fine with the plugging/unplugging of the Thunderbolt port. Now, every single time I have to reboot the Macbook Air to get the display to return to normal. Anyone seen this before? Does anyone have an answer other than resetting the smc and pram?