Needle Comes Unthreaded

I have a Baby Lock Model BLQP. I'm working on my second queen-sized quilt using the free-motion foot. Today I'm very frustrated. I was told to(and have been) pulling the bobbin thread through to the top, then holding both tails and sewing in place 2-3 stitches, then proceeding to quilt.

However, suddenly every time I start to go on and quilt, the top thread pulls out. I've re-threaded both the top thread and the bobbin thread and I know they are right. This has happened occasionally before, but now it's happened about a dozen times in a row and I have no idea what is wrong. Any ideas?

ANSWER

There are several reasons your why your thread keeps slipping out of your needle. Here's a few things you can try:

Consult the "troubleshooting" section of your sewing machine manual.
Remove dust particles and stray threads from your machine. Even a small piece of thread can jam the inner workings of your machine.
Check the machine tension. You might want to switch it back to the manufacturer's default setting.
This sounds crazy but, make sure your needle isn't installed backwards. The flat side should be facing away from you. Remember, also, to use the right needle for your particular fabric weight.
Check your bobbin. Is it wound in the right direction? Are the threads wound smoothly, without any loops or knots? Is it correctly installed in the bobbin case?
Is your thread spool facing the right direction? For vertical spools (up and down), position the thread groove at the top of the spool pin.

If you're using a horizontal spool pin, make sure the thread groove side goes on first (so it's on the right side of the spool). If you follow these rules, your thread will unwind smoothly.
Before you start to sew, place your needle and the thread take up in their highest positions.
Long thread tails are a must. Pull the top and bobbin threads until they reach the back of your machine.
If all else fails, you might want to change your thread. Cheap threads cause an array of problems. Always use quality threads that compliment the weight of your fabric.