How many texture layers can your card support? It looks like you have 5 on there. I don't know the technical term, but multitexturing with more textures than the card can process in a single go, can cause very odd errors, z-ordering problems too.
I had a problem where my top surface was being rendered below everything else. Try only using 4 layers and see what happens.
I had a problem where my top surface was being rendered below everything else. Try only using 4 layers and see what happens.