The black Apple pro mouse have some well known issues:
-Only one button
-Too flexible and short cord, which have a very high failure rate.
But I love it's sleek minimal design.
Mine has broken too, next to the mouse end and also at the USB plug. Since to open and to nicely refit the USB plug seems impossible, I decided to change the USB cable completely.
Step 1: Taking apart
There are a couple well detailed guide on the web about how to open and refit an apple pro mouse. But all of them only helps you when your USB cord broken next to the mouse's end. My cord has been broken on the other end too, so I have to change the whole cable. Also, I was fed up a bit with that very short cord.