The problem is that the phone after flashing a custom rom will work, but you get 'no carrier' meaning that the radio on the device isn't connecting to your carrier. In my case, 'Sprint'. I don't know why this happens, but no matter what I did, I couldn't get it to connect.
What I had to do was go back to stock. The MD4 stock didn't work for me, it would display the samsung note 2 branding screen, then the screen would fuzz out like an old tv that lost the vsync signal, and then the red light would blink blink blink. I bricked my pho.ne
The good news is, I didn't completely brick it. What you have to do is ODIN the phone. The problem was, it would never go into odin mode, it would always crash before it got there. What I had to do was take the battery out and power it ONLY via USB. Then it would go into odin, and I was able to flash the LJC firmware. It seems that if you want to replace the radio, you have to flash an entire rom to do it. Those downloads are a gig!
So even after doing this, it wouldn't quite work right. If you still have issues, you may have to ODIN a new BOOT image. Once you do that, then when it boots you'll get the standard sprint logo and animation / sound, but it will still hang. What you have to do then is load a custom recovery (odin), boot into that recovery, and format system twice then cache twice. The recovery that worked best for me was ClockworkMod Recovery v220.127.116.11.
That seemed to reset the radio/carrier and then I could load the original LJC rom & radio. I verified that I could access everything. Then, I did CF Auto-Root, and loaded a new custom rom. All was working afer that!