Experiment crashes on first use on a computer

I run medialab for experiments on 30 computers running either Windows Vista or 7. I create the .exp file on a Windows Vista computer in my office, then load it onto each computer using a usb drive. Sometimes (2 experiments out of the 5 experiments so far), I will set up all 30 computers, and load them all with the study files, and when I run the experiment for the first time on all the computers it will go all the way through the experiment until finished. However, while writing the data during that first run MediaLab crashes. The data file shows all the correct variable headings, but none of the data. When I restart MediaLab, everything works perfectly. This does not happen when I test/run the experiment on my office computer where I initially made the experiment. When this problem occurs, it happens on every computer without exception (except the computer I created the files on), and every computer also works the second time and everytime after that.

Has anyone had this problem, or know of what could possibly be going wrong?