Strange 1 pix white line between tiles on my 2D game

My game have a tiled 2d map.
This is a scene screenshot:
[9043-qq截图20130318172246.png|9043]

I found when I move the camera vertically, there are strange white lines randomly appeared between randomly tiles, See:
[9044-qq截图20130318172427.png|9044]

I don’t know why…

PS: This is a pixel style 2d game, so my texture’s filter mode is “Point”.

PS: I uploaded this test scene at https://dl.dropbox.com/u/53858613/Web/Web.html , Hold the left mouse button , camera will move downwards, then you’ll see white lines randomly.

Is there any answer here?

I solved my problem by repeating the same line to the sprite sheet.