Yesterday my machine was working fine. Today it is not. At first, it was sucking the fabric down into the little hole behind the needle (not sure what it's called) after a couple of stitches. I opened the bobbin case and it looked like the main thread was getting wrapped around the bobbin. I rethreaded it and tried a different fabric--it took a little longer to suck in the thread, but was still doing it. I changed the thread and bobbin to ones I was using yesterday (two different colors--I had been just playing around for practice), when it was working fine, and sewed on the same fabric. Now it's not sucking the fabric in or getting the thread wrapped around the bobbin--it's just failing to move after a few stitches and the main thread is turning into a tangled mess on the bottom while the bobbin thread doesn't seem to be going through at all.
If it helps, it's a Singer 2010 and used to belong to my grandmother (I asked for a sewing machine for Christmas, and she wasn't using this one, so it was free!). I don't know how old it is.