What are the formats on the Premiere Elements 11 Mac Timeline whose contents you are rendering to get the best possible preview? Do you have this problem with specific media source, and does the problem go away in a new project?
When you drag your file as the first file dragged to the Timeline, do you get an orange line over it or is there no colored line over it then?
If at this point there is an orange line over that content and you Timeline render, is that when you get the crash?
Or, does the crash occurs when you are doing a Timeline render because you have just edited one of the Timeline components? If this is the case,
what effects did you apply to the source and what edits did you perform on it?
If you go to the Adobe Premiere Elements Preview Files Folder in the Adobe Folder, how many preview files are piled up there?
Is your computer connected to the Internet? And, are you getting messages about rendering activation needed at the Timeline level?
Let us start here and then decide what next.