Hi Andy,
I am sure the aircraft textures do not control the cabin lights.
The Landing light switch in coopeartion with proper night textures can virtually turn on-off the tail lights, and any night lighting reflection on the fuselage. Textures do not do more.
I think the key is in the panel.cfg. Some panels (just as paywares do) have a different backbround image, and color setting for night lighting. I think that is badly coded or missing from the buggy panel. Maybe you should copy the whole PANEL folder of the working 737 onto the non-working one, and check the result.
It is just wasting time to search the bug around airplane textures

Errr...if you are talking about Virtual Cockpit...then textures does do the trick ! There, a new texture is required when you turn on the panel light. I was always talking about 2D panels before...