There are two similar bugs:
The LPC+crop bug started with ACR 6.1 and was fixed in 8.2.
The LPC mystery bug started with ACR 7.3 and was fixed in 8.6.
Both bugs cause repeated thumbnail extractions in Bridge on some images with Lens Profile Corrections enabled.
As you are on ACR 6.7 it can only be the first bug. The only workaround I know is to ensure that the crop does not touch the edge of the corrected image. A few pixels gap will do it. Also, it helps to keep less images in a folder--but this can't be avoided when using Collections or Finds.
I'd imagine that Adobe won't fix CS5 just for this. Presumably there's something in the smallprint which admonishes them from responsibility after the shelf life of the product ends. To be fair, it's not like they fixed it straight away in CS6, unlike the Bridge CS5 database bug (thanks, Adobe). They were only able to reproduce the fault in summer 2013.
I do not think this is a usable workaround for her, but let me get it straight: you are saying that for an image with lens correction activated not to trigger thumbnail regeneration, it should be cropped and the crop region should not touch the edge of the complete, original image after lens correction (i.e., whatever is visible of it when not cropped). Approximately (if one does not consider rotations), this simply means that it must be cropped of any number of pixels on each of the four sides. Am I understanding right?
What about uncropped but lens-corrected images? Are these somehow not a problem or the description above implicates that all lens corrected photos must be (even only minimally) cropped?
Thanks in advance,
The bug only appears when an image has LPC enabled AND a crop has been applied AND the crop touches ANY edge of the image. So it won't apply IF LPC is not enabled OR no crop has been applied OR a crop doesn't touch the image edge.
I went through a load of images moving the crop marks slightly away from the edges, and the regenerations stopped COMPLETELY.
No crop, no problem. It only applies to cropped images (with LPC).
Hope that clears it up.
Perfectly clear, thanks!