Strange normal map artifacts

ghaztehschmexeh

I'm trying to bake a normal map for a house I just modelled. I've done the usual - matched the lp close to the hp, uv mapped, smoothing groups by uv islands etc.

I can't for the life of me figure out why I'm getting artifacts such as the one below. Does anyone know what might cause this? Note: it's a flat surface.

Same result in 3DS Max and xNormal.

cheers

James Ordner

Post screenshots of the low poly and high poly, we may have a better idea of what's causing the issue.

Marcus_Aseth

I can't see the screen on the first post

ghaztehschmexeh

Triangulating the mesh seemed to fix it, which is odd.