This is really bad. I restored my Mac from Time Machine, after which everything seems fine.
However, Time Machine doesn’t keep copies of the thumbnails. This is fine, normally after opening Aperture after a restore, it will sit there and rebuild all the thumbnails (I have 50,000 images). But now, on MAvericks running Aperture 3.5.1, it will rebuild the thumbnails, but after about 1,000 images or ~10 minutes, the activity monitor will show all processor usage become RED (showing system processor use), and the thumbnail building hangs.
At that point I cannot even quit Aperture, and am forced to Force Quit Aperture. REstarting Aperture this point is futile, and it will bounce in the dock - I need to restart my mac.
After that Aperture runs fine again, but will continue its rebuild of thumbnails, only to freeze after the same amount/time.
I’ve tried repairing permissions on the Aperture Library, and repairing the library (not a rebuild - last I attempted this with Aperture 3.4+, it deleted all faces database and crashes out).