white line when snapping objects

hello everyone i just started using U3D-5 and i am building a house with "blocks" each 15cm by 1½ meters, but when i use the snap tool, "holding V" and snap em into place, i get a white line where the objects meet, like light escaping or something? the textures are 100% seamless, and tested in photoshop and what not... here is a picture of it, and this happens with every single texture i do this with.... very very annoying.