I had the same problem when I first bought mine. I had it back to the place where I bought it (they do service work on machines too) two different times and I was still having the same problem.
They ended up calling the manufacturer of the machine and found out there was a glitch in the manufacturing.
To fix the problem you have to put the feed dogs up before you turn your machine off. Then when you turn it on again you make one reg. stitch then drop the feed dogs and start quilting.
This has worked for me for the last 2 years and I've quilted about 20 quilts since then with no problem. Try it. Hope it works for you too. Bonnie