singer 9217 tension problem?

I own a Singer 9217 model and the tension has gone crazy all of the sudden. I was in the middle of a project and it was fine. While I was in the middle of stitching I noticed a slight catching on the bottom. When I finished my line I noticed the under side of the fabric had loose loops and thread nests where I back stitched. I've tried adjusting the tension and stitch length in both dirrections. Nothing seems to be working. Any recommendations or suggestions? I was told it would be 70-90$ to repair but I needed to finish my project this weekend. Thanks!