Samsung LNT4065 started flashing 2 weeks ago...unplugged to reset 2hrs later back to normal...made a call to Samsung about this problem...contact with customer service sent email with firmware to download (I printed and save this email as proof) said firmware will prevent problem in the future...put downloaded flash drive in TV...do you want to upgrade from this to this and I clicked yes...TV screen went totally black then off...will not power on...why?

It was not a firmware software problems,this problems was a hardware problems,the T-CON board that the board was starting to have a problems,but u reset the tv than tv was still use able because the T-CON board was still reset able.Than u made a huge error u listen and follow whom ever it was told u to force it in a new firmware software upgrade a new version was not compatible to ur tv.The tv now have a screw up new upgraded firmware software version is not working in ur tv main logic Tuner signal board.Now u only can do it is to tries force Samsung for a warrenty repair that all.The main logic tv Tuner signal board it is the tv problems now.

I'd say what you really needed in the first place is this:
http://www.ebay.com/itm/BN44-00167C-SAMSUNG-POWER-BOARD-REPAIR-KIT-/110735490949?pt=LH_DefaultDomain_0&hash=item19c8597f85

As to why it went dead...I think (and you should pray) that it's because the original problem just showed up again.

The original problem being the power board not functioning right and NOT what Samsung told you.

Chances are I am wrong, of course.

But I'd bet my lunch over anything any large company service rep reads you from a book.

http://blog.coppelltvrepair.com