Although a bit late now, when working on a project you should always save often and to a new file each time. Do not overwrite an existing project file.
When you do this you will always have a recent working copy of the project to drop back to in the event of a corrupt file. Obviously you won't want to keep every save so you can delete earlier copies but always keep the last few saves as a precaution.
Sadly if your project won't load it is likely corrupt, but you can try going into Preferences (CTRL + P) and lower all your graphics settings down to a minimum. Then close down CTA and reopen. Now try to load the project again. If it is the project size that is the issue you may find it will load now with the reduced graphics settings.
Peter
Forum Administrator
www.reallusion.com