Preview is broken and when exported in Nik Software plugin, it's black or over bright

I'm working on a project for a Sail championship (last month the J24 European Championship, while this week Interlaghi) and since I started the last one I've really great problems with preview and "exporting" in Nik Software, that I never had before.

This is workflow:

1. shot image in raw (Canon eos500d)
2. import image in Aperture3 (images are refered on external drive normally, but now for this project are refered on the desk, I've an 256[GB] SSD with 8[GB] of RAM)
3. edit the image with Aperture3 controls, if I'm not lucky leaving the full screen the preview (big) dissapear and broken (small)
4. if I'm lucky open the image in Nik Software (e.g. Dfine) and work on it, when finished if unlucky back to point 3
5. if not luck the image in Nik Software is Black
6. so regenerate preview, and similar action are taken (last night I've also rbuilt all archive, with cmd+alt click aperture icon)
7. if luck I can work and export
8. if not luck I must close Aperture and keep crossed fingers.

At the begining I thought it could be a problem of too many images in the same folder and aperture-project (1800), but this is not the first time I work with big volume (airplanes shooting in Axalp normally is 1200 shots in one day).

I thought even a speed problem on the archive (the externa HD is 5200rpm on FireWire).

So I decided to relocate raw files on the desk, as I said I've a 256[GB] SSD; but nothing change!

Maybe a problem on TIFF export??

Someone can tell me a solution? the only big change in my usual workflow is that now there is Analog Efex Pro (that I don't use).

extra: I'm using a MacBook Pro (after june 2009 version 5,5 )

Here I post some screenshots: