This would indicate something in your solution is causing a problem. You should look at the Runtimelog.txt to see what is happening. Do you have an endless loop that is causing you to crash? It could be almost anything but is most assuredly associated with your solution.
For some help in cutting your logs down to size check out this post:
Yes you are right, as I am using multiple loops in my solution and it is always giving the same error "OpenSpan.Runtime has stopped working" in code at the same position always. Even I have turned on the Diagnostic Log mode, but that log.txt file also does not explain the error.
You are likely reaching an endless loop or a stack overflow. Can you post a screenshot of your automation? Basically, a stack overflow occurs when you essentially have a circular yellow line that can go back to itself over and over. If you truly need an endless loop (or a while loop), use a ForLoop control and set the limit to -1. Since it can only increase, it will never reach the end until you call Break() on the loop. Using a ForLoop will also prevent a stack overflow as the stack is unwound at each iteration.