zarpman:
I feel your pain. Best Buy ended up sending a third party TV repair company . It took about week for them to get the part and I JUST got it fixed yesterday. To my surprise there is not much inside the TV. Just two not very big boards... one power supply board, and one main board.
They replaced the main board inside the TV and upon power up, the volume controls worked, but the OSD was blurry (like double image) with jaged edges. Previously I was playing with different versions to see what happens and that OSD blurry was one of the side effects. I told the tech about this experience. The technician agreed that this "just could work"... and we downloaded and tried A firmware per my serial number and still blurry, then tried B firmware and IT WORKED!! So my guess is that the 4th digit of your serial number has less to do with the actual main board, but possibly what type of LCD it is interfaced to.
Now its back to the way it was before my firmware update fiasco. The picture looks great again and all the side effects I originally mentioned are gone... however, I STILL HAVE a noticeable amount of latency, even in game mode. I also noticed the web site now offers a version C of the firmware which wasn’t there last week and has removed the installation instructions which were previously there. I'm considering trying the version C to see if I can get rid of my latency, but I'm afraid to try it... what if it happens again??? My wife was pissed the first time... I'm not sure I could handle a second. 
... meanwhile ... Its a pain to play video games and I'm back to square one.
The most frustrating part about all of this is if you call Insignia Support they don’t have any real technicians. Even the TV repair company commented on how hard it was to find the parts while still being unable to contact company technicians and being transferred to Geek Squad.
I hope Best Buy/Insignia (hopefully they read this) gets their act together one this.
So after using my shiny new TV for a couple of weeks, I figured I would come BACK and see if the firmware fiasco had been fixed. Why could I have just left well-enough alone? 
Seeing that there are now explicit instructions detailing whether to use firmware A, B, or C, I noticed that I am SUPPOSED to be using firmware C and not the tried and trusty B that has been keeping me happy. Figuring this would improve my picture even further, I jumped the gun. Now my refresh rate is horrible! High-speed stuffs (including sports and video games) are unwatchable/unplayable. This is both with Game Mode both off and on. Blarg.
Back to downgrading and upgrading I suppose.
