0xC0000005 - Access violation (Each time from a different dll)

I have been given a task to debug a C++ project. I have not written a single line of code in this project!!

This project executes for about 5 minutes without problem. Then it ends with an exception "Unhandled exception at (some .dll name) in EITos.exe: 0xC0000005: Access violation reading location "

Now every time I execute the program. The error is from a different dll. Sometimes it is a dll created by other programmers, sometimes it is related to QT. So I don't think this is a code problem. Is there any project setting that would affect this?

I am asking some general tips and hints as to how to debug this problem.