Trifid Nebula and Atik 314L+ Horizontal Lines. Help!

[gustavo_sanchez]

Saturday night I took this picture of M20 (Trifid Nebula). The equipment was my 8" F/4 Newtonian, Orion SSAG Mini Guider, Atik 314L+ Color CCD. 10 exposures of 6 minutes each. Can somebody please tell me why these lines are in the middle of my image?

Let me elaborate and ask another question. I am using Nebulosity to post-process the images. I do the bad pixel mapping, and then reconstruct the color images using the menus on the software. If I use the RGB option for reconstruction, the colors on the image look wrong (the pink part of the nebula looks green) so I used the CMYG option (which I not think is the correct option, but go figure). After I finished stacking and processing, I get these lines. What I am doing wrong?