Texture filtering / alignment problem

I''m working on (yet another) terrain engine. To allow for very large landscapes, I decided to split my terrain into "chunks". Each chunk has its own mesh and its own texture. The meshes fit together nicely, and the textures do fit together nicely when viewed in 2D in Paint. But viewed in DirectX, the borders are clearly visible: 

Screenshot 1

With the bilinear interpolation texture filter disabled, the problem is less noticeable, but still there if you look closely:

Screenshot 2

I have tried all the obvious values for texture coordinates, including:

(0,0)-(1,1)

(1 / TEXTURESIZE, 1 / TEXTURESIZE)-( 1 - 1 / TEXTURESIZE, 1 - 1 / TEXTURESIZE)

(0.5 / TEXTURESIZE, 0.5 / TEXTURESIZE)-( 1 - 0.5 / TEXTURESIZE, 1 - 0.5 / TEXTURESIZE)

etc.

But still can''t get rid of those visible seams!

Someone must have come across the problem before (after all my terrain engine is hardly a new idea!). Any ideas?