MediaLab v2006. freezing

Hello, I have recently had an issue with Medialab freezing in the middle of an experiment. The participant was towards the end of the experiment and the computer screen went blank (the blue background screen appeared with no questions or answers located on it). The only way to exit out of this screen was to force the shutdown of Medialab and none of the data was recorded. The questionnaire running when this occured was a normal scale response questionnaire with no skips. I tested the experiment on the same computer answering the questions the same way as the participant and the screen did not go blank again and the experiment ran until the end. We are currently running MediaLab v2006 on Windows XP.