I don't think this has anything to do with the scenery or the installation.
KDFW uses entirely custom runway lights, it's possible that after a flight, you simply had a problem with video ram corruption/exhaustion, so their textures disappeared just like any other scenery element could. Don't know why this affected only lights, but video memory corruption/exhaustion issues are really hard to understand, they just affect scenery items randomly.
The most likely cause for this (video memory problems after a long flight that), it's a memory leakage caused either by too high graphic settings, or an airplane gauges with memory leaks.