bloodshot I don't have the capx anymore, but I think I can make one up tomorrow..
basically you want to always make sure you are moving the tile only by 512 (or divisible) that way there can never be a gap or is the movement seen. but if you mean your player is reaching the edge before you move it then you need to increase your tile size.. so instead of 512, you'd need to make it 1024.
The other issue is to make sure the tile's starting position is already at a 512 or divisible x/y.