I also sometimes meet such phenomenon. Actually, I don't know why it happens. What am I doing when I meet this type of problem are.
- Use another machine. In my experience, though 32 bit machine cause such problem, 64 bit machine with more memory runs without crash. Reduce memory usage by another applications as less as possible.
- Change Result folder path in property of study. I had an experience that folder path change resolved a problem.
- Delete all temporary files including CWR file. It seems that sometimes existing temporary files cause problems.
The above ideas aren't based on any technical background because this type of unstability is very hard to find out root cause by user.