What used to be an occasional problem that was always fixed by Quitting and restarting Aperture, is now a consistent problem on every image returned by HDR Efx Pro 2 plug-in. Quitting and restarting Aperture usually corrects, but this is a horriblly inefficient way to work.
Aperture 3.4.3 on Mountain Lion 10.8.2.
27" iMac 2.93 GHz Intel Core i7
16 GB 1333 MHz DDR3
Image library (managed) located on a Drobo Pro mounted via iSCSI.
MacBook Pro 17", Mac OS X (10.5.2), Lots of external FW800 drives