Maytag washer is full of water on the rinse cycle and it stopped. Power light isn't on and can't change cycles. Breaker switch is okay... all other appliances are working. What could have caused it to stop running midcycle?

You are having problems with the water level control or the timer, more than likely, but you also need to test the lid switch and find out what is stopping it. You will need a good digital multimeter to test everything. First, drain the water and remove the back to the controls and on the water level control you will see a plastic hose attached. Follow it to the bottom of the tub and check to see if it is attached. It may have come loose and if so that is your problem. If not, then remove it and blow on it while listening for the switch to click. If the switch does not click then replace it, if it does then check it with a meter. You have a common wire coming into it and with no pressure it sends power to the water valves by closing the switch to them. On the meter set to "ohms" it will read about zero (unplug one wire, like the common wire and never have power on when doing any test on "ohms."). When you blow on it the switch will open the contacts to the water valves and close the one to the timer. I bet that the contacts are not closing to send power to the timer, if it is sending power to the timer then you may have a bad timer. When you re-attach the hose, cut off about 1/4" on each end to get a good connection. Here are some manuals: https://dl.dropboxusercontent.com/u/8010163/Understanding%20automatic%20washer.pdf
https://dl.dropboxusercontent.com/u/8010163/How%20to%20use%20Test%20Equipment%20Service%20Manu al.pdf
https://dl.dropboxusercontent.com/u/8010163/Maytag%20Washers.zip