Breadman TR2200C Doesn't knead
I have this bread machine. A few months ago after several years of use, this exact problem happened with my machine. I opened up the bottom (easy to do, just keep track of the screws) and found that the belt had slipped off the pulleys. If you read the reviews on Amazon, you'll see that this is a common problem with this machine.
It's pretty easy to put the belt back on, but that may only be a temporary fix. Mine kept hopping off, until it got to the point where I just left the bottom off my machine to make the belt easier to access.
A few things might help. First, put a thin coating of vegetable oil on the belt before putting it back on the pulleys. This was recommended to me, and since I did it, the belt hasn't come off again (about 6 loaves; before that, the belt jumped off nearly every loaf). Even if you're skeptical, try it.
Second, the pulley tension is adjustable. If you loosen the 4 screws around the little pulley, you can move it slightly to increase or decrease the tension. Be careful - if you tighten it too much, you'll stress the motor and it will labor and stall out. Also, too much tension seems to flex the big pulley, making it more likely that the belt will slip off. You may find that the solution is to reduce, not increase, the tension.
Third, someone on Amazon solved the problem by making a cardboard disk that's slightly larger than the big pulley, and arranging this somehow to keep the belt from coming off. You could try this or some other method of blocking the cut-out areas in the edge of the pulley that allow the belt to come off.
On the down side, if the belt is actually broken, you're going to have a tough time replacing it. Parts aren't available from the manufacturer or anywhere else for that matter, except used parts on eBay.
If you can solve the belt problem, I think you'll love the machine. It makes terrific bread, much better than the one other brand I've used.