Granted, I'm just setting up the lighting and I haven't given the models normal data yet. That said, I'd expect the models to be fine with that; they'd just be black.
I've also enabled the GL_NORMAL_ARRAY client state. Haven't initialised the normal pointer yet, though. Again, I'd expect this to be fine and I'd have unlit models. Could be the cause of the problem, I guess.
One other thing. If I omit that line (the GL_LIGHT0 one, that is), my models are black, as I'd expect. And I can enable any of the other seven lights just fine.
Note: Final terrain won't actually look like that - it's just a randomised height at the moment as I haven't implemented the correct algorithm yet. The idea was to build the renderer from the ground up first.