Maybe we're on the right track (RigManager connection, laptop hibernation and so on). Right now I'm tweaking a little and unplugged the USB. After over an hour still no problems at all.
I had the same problem last rehearsal: FW 4.0.5, Performance Mode, Remote, MacBook and Rigmanager connected. I'm not sure if the MacBook went into energy safe modus in the moment the Kemper crashed...