Do you ever move your mouse, and your mouse cursor stays in the same place? If so, it might be time to clean your mouse. No, that doesn't mean you give it a bath. The ball in the bottom of your mouse will roll dust and lint into the mouse case itself. This eventually will prevent the mouse from working properly.
A cordless mouse requires a little additional care. If this mouse starts acting funny, and you've cleaned the ball, it is probably the battery in the mouse or the receiving unit. Replace the batteries and all should be well.
However, before you jump to conclusions, check and make sure you don't have a lot of stuff piled up between the mouse and the receiver. This would prevent the infrared signal from getting from the mouse to the receiver.
It is also a good idea to keep your mouse pad clean. Dust it off occasionally, and keep it free from debris.
If your mouse suddenly stops working for no apparent reason, you might have recently installed new software or a device driver that could be interfering with the operation of your mouse. Check the manual of the new software you installed to determine how to resolve COM port conflicts.