52Z5100 here. Same issues as described above. My manufacture date is June '09. I spent about 2 hours on the phone yesterday, eventually making it up to 3rd tier support in CA. This guy seemed set on blaming it on my router, that it was somehow blocking the TV's connection to the internet. I told him I don't have any issues with the 3 laptops that are connected wirelessly to it at all. I hooked up a direct "wired" connection to the router and still received the same <5006> error.
I believe the left hand is not talking to the right at Sony. Apparently, as stated above, this issue has been successfully resolved by moving a TV's MAC address out of their content database and back in. I can't understand why Sony is not passing the word to their techs to implement this fix! I, like otheres want to make sure this new TV is working correctly before I decide to ship it back and get a replacement, only to find out the replacement doesn't work correctly either.
/////////////////////////// UPDATE ////////////////////////////////
My TV Widgets are now working!! I like the Widgets options also. More detail: I called Sony back after the above post to try and track down this MAC address issue. I had the problem number from yesterday's call and I was determined to get to their third tier support again. The tech support person wouldn't transfer me directly until I went through the whole process again of telling her how I had my TV connected to the internet. I said I have a static IP assigned to my Linksys Bridge and the IP address is in the DMZ on my router. This means the bridge/TV has direct access to the internet without the router firewall in the way. I also told her my TV was updated with the latest Firmware 109pn. I confirmed my TV connected with the internet, but the problem starts when you try to download/update video content. The TV will go through "Authenticating" and get to updating content. I reasoned that if it gets past the authenticating part, it's obviously communicating with the Sony server.
She then asked me if I did a Reset, and I said no. She said I did that yesterday according to one of the previous Techs post in their database. I said no, but I'll give it a try. She instructed me turn the TV on, hold the UP arrow for about 10 seconds, then use the power button ON THE SIDE OF THE TV to turn it off. The TV re-booted and came back on. I then set all the settings for the TV as if new and proceeded to update internet video content and sure enough, it now works!
This Monday will be the first week of ownership and I was starting to get frustrated with this. I thanked the Tech, but left her with a customer opinion that Sony should acknowledge there are a number of customers out there having the same problem and they need to work a little harder at resolving this customer concern.