Never heard of it. Which of course doesn't mean it couldn't be an ML issue. Going to guess you have tried, but I personally would start off with running the PP session over and over again to see if you can get the error outside of the MediaLab context/environment. I would also, of course, turn to our ever-handy Google to look for hits re "PowerPoint erratic behaviour" or some such. Please let me know how it goes if you learn anything on this--very odd! Hmm. I would also check to see if it replicates across machines and maybe also check to see if the same PP show does the same thing when embedded in the first sample that comes with MediaLab--i.e., perhaps replacing the PP show used in the second condition of that sample. Good luck!