Hope Samsung Tech can help or anyone else:
I live in Israel and have an LA52B750U1RXSQ. The TV is connected to internet through a LAN cable and the network test always passes without a problem. I used to be able to connect to the internet and use the YouTube widget but after a factory reset, done by pressing and holding the exit button on the remote for 10 seconds, the internet@tv has stopped working.
Network test passes without a hitch, but when the internet@tv button on the remote is pressed I get after a short "Starting", then short "downloading" message the error message "network error". It's NOT "network interference" and NOT "service not supported". The router settings have not changed, and it is a Cisco router.
Again, it WORKED before, but after a reset with the exit button held for 10 secs it stopped. It has the latest firmware provided on the Israeli Samsung website, version 2006 from Oct. 2010.