Samsung forum: Firmware Update for LNT4061FX/XAA Causes Problems

I had same problem and if you call Samsung support they claim there is a warning on the download site which I have yet to see. Be WARNED do not update your set unless specifically told to do so by samsung they claim it can invalidate your warranty!. There are also couple of other things to check. Make sure the SCREEN SIZE is correct: Panel Option = 46AMW for LN-T4665 displays, and 46AM for LN-T4661 displays.
Make sure that if you own an LN-T4x65 that your Lvds Tx Bit = 10bit.
Make sure if you own an LN-T4x61 that your Lvds Tx Bit = 8bit.
If you own an LN-T4x65, your should change your model so it says "Tulip Side."
If you own an LN-T4x61, you should change the model so it says "Tulip."

To access this menu:
0. Set the TV onto an unused source so you have a black or blue screen. This makes reading the menu easier in later steps.
1. Turn the TV off.
2. On the remote, press MUTE, 1, 8, 2, POWER
3. The TV will turn on into service mode. It takes a few seconds after powering on to display the service menu.
4. Using the arrow buttons on the remote, go down to Option Byte and press Enter.
5. Arrow down to "Lvds Tx Fmt" and press Enter.
6. Using the right and left arrow buttons, change the setting. Mine was set to JEIDA. Setting it to VESA fixed things.
7. Press Menu to exit.
8. Turn the TV off to apply the changes.

Upgraded the firmware a few weeks ago to my 32 inch samsung and the 40 inch one. The 32 one went fine the upgrade to the 40 inch one failed with all the garble. After calling samsung support they only offered me to parts but no labor. I was almost giving up looking for another tv to buy when I found your post. Tv is working fine now. Thank you.