Strange “Program Error”

Only one of our users is reporting this problem, and then, only on a handfull of their PCs…

“xxxx.exe” has generated errors and will be closed by Windows”.

The error occurs once per day at most, and sometimes, only once or twice per month (they say no background tasks are running at the time the error occurs). When the error occurs, our application is generally idle… the user is in Outlook or some other program, or not in any programs at all (everything is minimized to the task bar).

The Dr. Watson log is pointing at our app, but I cannot tie anything in the log directly to our program.

This handful of PCs is at the SP4 level.

Can anyone offer suggestions on how I can track the cause? How can an idle program cause a memory exception?