If you want a good answer fast then put the time in and give a lot more detail!
What version of AE are you running?
When does the crash occur?
What is the type of project you are trying to render (2d layers only or 3d, what effects involved...).
AE projects on windows should work with no problem on the mac.
Are you sure you have the same version (or higher) of AE as the one the project was made in?
Do you have the latest updates?