@ossobuco,
If it were a PC, I'd tell you to reboot the computer. If that didn't work, I'd tell you to power down the computer, unplug the mouse from the computer, blow on the plug and replug it back in.
Doing the mouse unplug trick often eliminates the bubble of static electricity that sometimes forms between the connections. Since we're having many thunder storm warnings in the area today, static electricity could be the culprit.
Have no idea if it works on an Apple creature.