Since the upgrade from Aperture 2 to 3, I was struggling with a slow and often hanging system. The moment Aperture was turned on, it was as if the entire system would go into a momentarily lapse and then sort of freeze.
I tried many things. The first was – as recommended by most website – to turn off the faces feature by removing the check from Aperture -> Preferences -> General – Enable Faces . While that stopped it from searching through my entire photo collection for faces, it still didn’t resolve the issue of overall system slowness.
More searches lead me to various other discussions and after trying several things, this is what has finally made Aperture work happily on my Macbook Pro :
I deleted all the files in :
Hard Drive/Users/(Your user)/Library/Caches
The I also deleted this file:
Hard Drive/Users/(Your user)/Library/Preferences/com.apple.aperture.plist
After this, I emptied Trash. Some files would not empty from trash because they were in use. I continued deleting till all other files were deleted. Then, in the Finder menu, I used the Secure Empty Trash option to delete the pending files from Trash.
When I restarted Aperture, all my settings were set to default. I created a new Library and re-imported all my pictures. Thats it, Aperture has been behaving since then !