If you're using fizzler_left and fizzler_right textures make sure that the brushes are only 64 units wide. But you can't fit the brush in then. Set texture scale to 0.125. This will take care of any lines resulting form those brushes...

I tried "fit" in the texture tool as well, didn't solve it but did make it look a little better.
In hammer I don 't see anything wrong.

I might actually know this one! :D Make sure to use the texture application tool to ensure that the texture is centered on the brush. Also, can you see the line in Hammer?

I think that might be a problem with the texture itself, I've seen it on a number of fizzlers. With the brushes, you should be clipping them into 128x64, 128x?, 128x64 sections and applying the underground_fizzler_wide textures to them, and choosing Fit. In the picture you can see the semicircular emitter effects are stretched.

well, I do and want to fix it :P

Easy fix is to just not look at it. Hardly anyone will ever notice it. I didn't.