Let's face it, the main attraction of BSF is building your own ships. Share them! If you need help, check the Shipmaker Info & Help forum a little ways down.
IIRC it's usually caused by mirroring depthed weapons, (and maybe modules) though it also seems to pop up randomly from time to time.
Normally reloading the ship, messing around with it and saving it again should solve it.
Well I found out what the problem was.
I was stuffing around with turrets and drivers trying to figure out how they work, and something must have stuffed itself.
I deleted the section that I had experimented with, and it worked perfectly!
The shape is cool, and the general design is good.
My only two criticisms are the liberal use of the "Generic" sections, which lack fine details and don't look good in large quantities. Also, the holes in the ship make it look very fragile and don't look good in general. That's not to say holes are inherently bad, but here, they don't look good.