i have a non-retina 2012 macbook pro running mountain lion.
whenever i take it back and forth between home and work it will not automatically pair with my mighty mice (one at work, one at home) or my magic mouse (in home office). it will automatically pair with an apple trackpad. when i boot the computer no matter how long i wait the mice will not work. as soon as i click, though, a dialogue box pops up: