what the hell is wrong with my sewing machine?!

[littleweirdgrrl.livejournal.com]

My sewing machine was working fine, and then it spontaneously decided to start collecting a huge mess of thread on the back side of the fabric. I tried playing with the tension and nothing happened. This has happened before and I can't remember if I did anything to fix it. At this point, I'm out of ideas, and the sewing machine won't respond to my yelling.