The problem is the file is just too big. What you have to do is separate it into separate files, maybe each side, front and back. Or you can resample the raster images with less dpi.
What I do when that happens is delete objects till I can save, then I undo the deletions, delete what I saved then try saving again with a different name. And keep repeating the process till everything is saved in separate files.
The next problem you will have is that flexi will rip and rip and rip then print nothing (this is in 8.6 have not done anything large enough in 10.5 yet) this happens to us when using large high res files now and then. When this happens we need to use versaworks to print the job.
Hope this helps you guys.
If you uninstall and then reinstall, be sure to install into a new directory.