MediaLab freezes, running on Vista

[braseg]

We are building a study that includes a large number of variables (multiple personality instruments), and are having a problem with MediaLab freezing up after about 150 items. Specifically, after an arbitrary item it will go to a blank purple screen and nothing new will come up. We have found a few clues as to what is going on:

1. It does not happen on a computer we have that is still running MicroSoft XP. It only happens with Vista
2. The ctrl-alt-right arrow will exit the program if done immediately, but if one continues to press keys after reaching the blank purple screen it will lock up the program completely.

Any thoughts?
Thanks