Software Conflict?

I am running/trying to run an experiment that has 4 conditions on a single machine (Vista is the OS). In the beginning, ML runs through several questionnaires, and then it switches to DRT to do a timed sorting task, and then it switches back to ML to collect demographics. Without explanation, ML has been crashing during the first set of questionnaires--no consistent pattern, no specific questionnaire or item--on three of the four conditions I'm running (the control and two of the experimental conditions have failed at various times). The crashing is not consistent, itself; when testing it, I can't always get it to crash. However, it crashed on all my real subjects today and half of them on the previous couple of days I have been running. When it crashes, it goes to a blank light blue screen and I have to use Task Manager to stop it (ctrl+alt+right arrow doesn't work).

I have cleared out the data files so there's no conflict with subject numbers. I have tried running through all conditions and they all run at least some of the time (!). I'm wondering if this is a conflict between something else running on my operating system. I don't have any other windows open, but up till just now, the Sidebar was running, for one, and the computer occasionally searches for a wireless network, which I have also turned off. Any thoughts or suggestions? I could not find this exact problem elsewhere but I didn't make an exhaustive search.

I discovered in this meantime that the program does not crash if I exit MediaLab between running subjects.

Here's my speculation about the cause of the problem: Because DirectRT does not write data while the program is going on, is it possible that those data and the subsequent items (demographics at the end) in MediaLab are burdening the computer memory in a way? That somehow if I include a specific write command at the end of the DirectRT task that maybe it wouldn't work? MediaLab is rather unstable at the end of the experiment (it flashes to the wallpaper background in between responses to questions).

The fact that restarting MediaLab between sessions does suggest very much that it is some kind of memory/system burden. What versions (200x.x.x) of each program are you running.