When an ice maker stops dispensing ice and you check it only to find a huge sheet of ice, you have a problem. Even if you make the effort to thaw that sheet of ice away, chances are it is going to come back the next time your ice maker does its job. As you thaw the ice, you need to deduce why this issue occurred in the first place.
If your ice maker is covered in ice, you have an overfilling problem. Too much water is being let in, and as such, it overfills and becomes covered in ice. When this happens, there are two potential issues.
Low Water Pressure
If your home has manifested low water pressure, it will affect your ice maker. The water inlet valve needs at least 20 psi to work properly. If it is not getting that water pressure, then the valve may not close all the way when it stops flowing. The effect of this is that water will continue to slowly drip into your ice maker, overfilling it and freezing it. Check your water pressure to determine if this is the problem.
Defective Water Inlet Valve
If your water pressure has checked out, you should look to the water inlet valve itself as a cause. Before considering it defective, you may also want to consider that if you have hard water, this issue can be caused by mineral build up as well.
If there is no build up, only then should the water inlet valve be considered defective. It could be that your water pressure is fine, but the valve itself is not closing properly anyway. If this is the case, then the water inlet valve will need to be replaced to prevent overflowing in the ice maker.
If you are not comfortable doing this or believe your water inlet valve checks out, you may want to seek professional appliance repair.