craftgrrl | UGH STUPID MACHINE.

There's something annoyingly wrong with my sewing machine, guys. Please help me figure out how to fix it!

It's a brother XL-2230 as shown here:

I've never had a problem with the machine before and today I decided to make myself a nice tote for my knitting things. I started it up and good ol' Bro was working fine - I sewed up three sides of my outside fabric. But when I moved on to sewing up the lining, the bobbin began to squeak and the well the, "roaring," I guess, of the machine got louder and softer. The stitching however looked fine on top so I just kept going. Unfortunately when I turned the fabric over, all of the bobbin thread was really loose and tangled and ugly.

I just right now tried rethreading the machine, but it didn't help in the least. I did it again and it still didn't help. So I removed the bobbin again and the bobbin case is really loose. I can move it around with my finger. Is this supposed to happen? Does anyone know what could be wrong?