To help us reproduce this strange keyboard issue and track down the cause, could all of you please answer the following questions and send me an email in your convenience ?
(1) What's your Mac model, OS version ?
(2) What slideshow mode you were using ( Presenter Mode or Mirrored Mode) ?
(3) Were your Mac connected to an external display or projector ?
(4) Were you using a USB presentation remote ?
(5) Were you using gfxCardStatus ?
(6) Were your Mac connected to network then ?
(7) How long you have to idle to reproduce the issue
(8) Have you installed any PowerPoint add-on ?
(9) Have you seen any notfication popup or alert (such as ones from OutLook or Calendar) during the slide show
(10) What's your Mac's Screensaver and energy saving settings ?
(11) Were you using "Growl" ?
(12) Were you using "DropBox" ?
(13) When running into this keyboard issue, try first click the slide using mouse. Will doing so solve the keyboard issue ?
(14) Was your Mac on battery or plugged ?
(15) How long PowerPoint has been running ?
Many thanks and really sorry for all the inconveniences. Really wish you could take some time to answer above questions. It will help us a lot. Somehow we are not able to reproduce this strange KeyBoard focus losing issue.