Baking Problem

Hi 

I am have a problem trying to bake my meshes in Sub Painter. I have never had this problem before and I have been trying for a number of hours to try and fix it to no avail. In blender all my objects are unrwapped with their own textures. None are overlapping because they are seperate. Nothing shows like there is an error in Blender its only when I bake in SP. I have narrowed it down to two meshes 1) the main wall that you can see in the image. 2) a window frame that appears in the top left. When I leave out the window frame, the rest of the meshes bake fine. It's only when I include the frame do I get those nasty lines on the main wall mesh. Obviously it has something to do with the window frame but I cannot work out what. I have even deleted it and duplicated the window frame from the right side and still it happens. Hope somebody can help?