Yeah power of two doesn't help. I've tried almost every number here. I wouldn't think that this was how this was designed to work. It would seem that it should work with any scale factor but it just doesn't.

Is it possible that the UV coords of the HMP format are just screwy? I noticed that this is a problem even without shaders. I then made a model out of two polygons, planar mapped it with the same texture, lined up bunch of them up in wed and the textures tiled perfectly.