Odd one this. When I disconnect the power from my MacBook I lose my magic mouse connection. I get a pop up from parallels 'entered power save mode' and then it won't connect again until I'm on mains. I've only just switched from Fusion to Parallels and this is the only change I've made since the issue started. I'm running Desktop 10 on Yosemite Beta so appreciate support might not yet be available whilst I'm running on a beta OS but thought I ask in case anyone had any suggestions. Cheers Joe.