Does it stop at the same point in the print? If it's exactly the same point, then it's probably not a coincidence, but something to do with the G-code itself. (And there's been at least one other report like this that turned out to be a power saving mode mysteriously activated on the computer.)
However, most problems are related to USB and and caused by electrical noise and ground loops causing the USB to disconnect momentarily -- and it doesn't recover on its own. If you have changed, or even moved, the USB cable, that could be it. Also, power supply, or even having plugged the laptop or the printer in a different outlet. I've had problems with a new fridge killing my USB connection every time the compressor cycled off. I suspect A/C units can do the same thing, and, if you're in the northern hemisphere, it could be that you've just started using your A/C.
I've tried various combinations of grounding the printer, a floating power supply, RF suppressor ferrite cores on the USB cable, a better quality USB cable... The floating power supply made no difference. Everything else made interruptions less likely: connecting the signal ground (supply V-) to earth ground; USB cable coiled through the ferrite core several times; shorter USB cable; better screened USB cable; moving the fridge to a different circuit. However, even doing all of them did not solve the problem completely, at least not for me. The only two solutions that worked are: printing off SD card (no USB connected at all), and optoisolators on the USB. You can read more about the latter
here and
here. Several other people have done it, and it seems to have helped.
Of course, there's the possibility that installing that LCD broke something on the Mega. The RAMPS is practically indestructible, electrically speaking, but it could have a flaky connection that's been made worse -- but that's unlikely, given the symptoms.