Are you sure the zipper foot is attached properly? I have a Brother machine, too, and I hate the way the zipper foot seems to just hang there. Mine is a little tricky to make sure it's attached right. If it's attached all the way and you're stitching up against the piping, but without it under the foot, it shouldn't give you any trouble.

Donna

Now that I've spent about 4 hours with my machine trying to fix the problem, I don't think the zipper foot is the problem. I say that because I switched back to the standard foot, and the tension problems still remained. I tried changing the bobbin and the needle, but nothing worked.

According to my owner's manual, because the bobbin thread is showing through, the upper thread is too tight. I loosened it by turning the dial the next step down, and then the bobbin thread was way too loose. It seems that if the bobbin thread is correct, the upper thread is too tight. If the upper thread is correct, the bobbin thread is too loose. Any ideas?

You can tighten the bobbin tension and see if that helps. There is a tiny screw on the bobbin case - turn it just a bit to the right (no more than a 1/4 turn)and try again.

Donna