Permanent Binding Order Solution:
I believe you are experiencing intermittent connection problems with your Thunderbolt Display Ethernet interface because your binding order needs to be configured properly, as follows:
• In Lion, go to System Preferences > Network > select the Gear drop-down-list button located immediately to the right of the plus [+] and minus [–] buttons > then select Set Service Order...
• In the Service Order list, drag your "Display Ethernet" interface to the top of the list > select OK
• select Apply
Technical Explanation:
In the world of networking, "binding" means to "listen," so by placing Display Ethernet first in the binding order, you are asking Lion to listen first on the "Display Ethernet" interface before it listens on your "Ethernet," "Wi-Fi," or whatever other interfaces you have going.
This way, for example, if you still have Wi-Fi turned on whenever you dock your MacBook Pro—which I would want, as a matter of convenience—then Lion will use your hard-wired Display Ethernet interface before it tries to use your Wi-Fi interface.
This explains the hit and miss user stories and excruciating wait times for a connection that everybody is experiencing—depending upon their binding order. The most likely reason everybody is having connection issues with their Display Ethernet ports is because they have Wi-Fi listed before Display Ethernet in the Service Order list.
In this Wi-Fi first example, then Lion will continue trying to connect using the Wi-Fi interface for a certain pre-determined time period until that period times out, then Lion will try to use the next interface listed in the binding order for its time period, and so forth.
Every network operating system out there has to be told which interface to listen on first and Lion is no exception.
