When you rebuild your library, Aperture has probably discovered an orphaned image that had old-style "Curves" adjustments. When it added that image to the library again, it also reintroduced the old-style Curves adjustment.
One way to get your own "Curves" adjustment back, would be to select one of the recently adjusted images and save that adjustment as an effect (In the "Effects" menu -> "Save as Effect").
--Kirby, possibly blinded by all the snow we've been having.
I saw your beautifully framed snow-picture in the other thread. And we have plenty of snow today too, so we are in this together.
Kirby, I think what is happening is comparable to the problem with the Highlights & Shadows brick. If the Aperture library needs the olde-tyme Curves, because it contains an image, that has the old adjustments, then we will see the older "Curves"
So I doubt that reinstalling will help, because the effect depends on the image versions in the library. A new library would help in this case, only how to transfer the contents of the current library to the new library, without the one image that has been causing the reversion?
wouldn't saving as an Effect save and apply the parameters and not the "auto" algorithm?
My hope is, that this will save the new new effect, - like in your tip in the post above.
But I have never seen this happen to the Curves, so I am open for all suggestions.
Did a little troubleshooting work:
I didn't reinstall Aperture, but I did trash the Preferences, but problem persisted.
I restored a previous version of the library file and all of those curves were ok (i.e., did not "reset" to the old style nor remove the auto-generated S-curve).
Chose one image that had previously been adjust with the Auto-Enhance effect and changed the curve to the old style by option-clicking the auto-luminance button. I checked other images and they remained unchanged. So the presence of the old style curve on a recent image doesn't mess with other images.
On this restored library file I repaired the database. All images remained unchanged.
Then I rebuilt the database and they problem reappeared: images with the auto-enhance effect changed the curves adjustment.
Weird. Looks like I'm okay as long as I do not rebuild the database.