If I use Bridge CS4 on a directory and subsequently open the same directory with Bridge CS5, Bridge insistes on rebuilding thumbnails and previews (as indicated on the bottom status line). If I subsequently reopen the directory in Bridge CS4, it again rebuilds thumbs and previews - however only thumbs seem to be rebuilt. The Preferences in both versions of Bridge are "identical". The bridge cache files are maintained in the image directories.
The cache construction seems to be quite fast (faster than anticipated) - I am not sure what, if anything, is being rebuilt.
Is this an expected operation?
This presents some difficulties in that I have 530,000 images (7 terabytes) on Bridge CS4 and the reconstruction of the files would literally take weeks to rebuild.