Aperture frozen on "loading assets"
Recently upgraded to Yosemite and Aperture 3.6. Never had this problem prior. Aperture, when importing camera card (or from iPhone) is frozen on "loading assets". Sometimes I see no previews of photos and sometimes I see a few previews but am never able to actually hit import button. I've tried rebooting, I've tried opening up more hard drive space, I've tried to import to different locations, I've tried importing from my iPhone: None of this worked. Please help.
Aperture 3, OS X Yosemite (10.10)