We have run 35 participants through an experiment. For 2 of the participants, the screen went blank after answering questionnaires (just after watching a movie) right before a Direct RT task was supposed to begin. The screen went blank and could not be advanced using secret keys. The only way to clear the screen was to terminate the experiment. Nothing seemed to work. We have 4 versions of the same experiment to represent 4 conditions. We are not sure if it is a coincidence that both participants were in condition 3. We tried running condition 3 later on and the error did not occur. Is there some bug in the system that we need to resolve?