Jeffb3 mentioned on another topic earlier today that he has seen problems with EMI interference when using the SD card, and I thought that was another possibility for your problems. If the noise is causing your data to be corrupted, then Marlin could hang based on what it is reading. The only thing that does not fit is your hanging is happening in roughly the same place. I would expect a more random hanging if the issue was noise. While Jeff did not specify, adding shielding to your LCD cables might solve such a problem.