Ok , I thought I had mentioned what version I am running, sorry about that its been so long since I were in theses forums.
I have A5 Commercial edition version 5.240 / wed version 5.3.
My video card is a "NVIDIA GeForce FX 5700LE"
I have been at times having a single light source in some rooms and I have been known to mix different resolution textures.
I hope this helps you in working out whats happening or understand what the problem is, please reply as soon as posible thanks :-)