I had this happen the other day when I went for medium resolution AND a high-value procedural bump map. The scene was fine when rendered with a lower bump setting and/or no skylight and/or low resolution.
I guess the answer is that you may be at your machine's limit.
I did a work around by  using a working version of the scene to delete everything not in the actual shot. Even better was reducing the bump.
Oh, not to forget: When a crash like this happens, Carrara has left behind somewhere a temp file that may contain GB of useless data.  It doesn't interfere with the program but uses up disc space.