Hi there,
Just thought I'd add my case to the list here and update with some new info.
I too have experienced the issues after updating to the latest 5.1 software, and like others the issues only appear when the ethernet cable connection is active, no issues at all via wifi.
Issues that occur: Cannot connect to WSJ, MLB, NHL, or PhotoStream. I don't use iTunes Match so not sure if that works. Connecting via wifi works perfectly.
Resolutions attempted: Restore via device itself over ethernet, no joy. Restore via device itself over wifi, no joy. Restore device via USB through iTunes on iMac, still no joy. Restore the previous software 5.0.2 and everything works perfectly!
Called Apple, did another update and restore and not working. I was told to go to Genius Bar at the Apple store and probably exchange after they tested. I did that, they were able to duplicate in the store and therefore exchanged with a new unit.
I brought the new unit home, and exactly same problem. Works fine on 5.0.2 but as soon as 5.1 is installed the ethernet does not work on the above applications. Oddly iTunes and Netflix and the other "channels" work fine, just those ones seem to be affected for some reason.
So CLEARLY there is an issue with the 5.1 software. I have downgraded the new unit back to 5.0.2 as a work around for now since I need ethernet connection and wifi is not good enough where it is installed.
I REALLY hope Apple fixes this soon. The shared PhotoStreams is a great feature that I would like to use!
To everyone out there: its a software problem and exchanging with a new unit does NOT resolve the issue. The new software works great but on WIFI only. What a disappointing experience this has been with Apple for me. I would expect this lack of testing and carelessness from Microsoft, but not Apple.
...sadly disappointed,
D.