Wonder if you pushed a button or something like that to lower the feed dogs.

id guess it is your pressure foot setting and/or lint as well.

Does it only do it at the beginning of the seams? Do you use leaders/enders? I have found that with thinner fabrics I get that too sometimes. It's a habit for me to use a leader and ender every time though. It drives me batty when I can't (like when sewing binding on-I still use one but not in the usual way).

I had about the same problem last week.I called a dealer and they told me to rethread my machine. Try rethreading everything and see if that helps. Let us know.

Could be lint between the feed dogs and the stitch plate. Remove the plate (area where the needle goes down through) and clean well.

If you're working with flannel, the feed dogs may be full of lint. Check to see if those little grooves are full of stuff. You'd be surprised how smooth they can get when you are working with fluffy fabric!

Most likely you need to take the plate off, and clean underneath it--bet it is stuffed full of lint!

when all else fails, re-read the instruction booklet. I have found I overlooked some thing when first reading.

Take off the plate under your foot and clean the grooves between. I had this problem and found a ton of lint in those grooves. Now I make sure I check these everytime I clean my machine and it works great.

My first thought was lint. I was amazed by how much lint was in my machine the first time I opened it (I bought it used). It was felted between the feed dogs. Now I clean and oil religiously.

Also check the thread length and if you accidentally dropped the feed dogs as has already been mentioned.

Cheers, K