CA Quest optionally uses Phil Harvey's exiftool to build a database of your images and their Aperture and ISO values. You must install exiftool on your default path, or in the same directory as the main Bibble executable (e.g. bibble5.exe). To download and install exiftool, see http://www.sno.phy.queensu.ca/~phil/exiftool/install.html.
To build the exif database, just click the "Update" button next to the checkbox "Extended Image Info Database", and choose a directory which contains your images. This should then kick off a console process running exiftool. If successful, there will be a new subdirectory in your Bibble data directory called "CAQuest cache", containing a number of small .xml files, one for each image with a distinct date/time. (You may see a few warnings from exiftool - these are for duplicate files, or files with the same date/time to within 1s).
You can re-run the update at any time, or for any number of different image directories, although the database directory may get quite large if you process all your historical files. You can also delete the database and re-create it at any time if you want to tidy up a bit. Just don't delete the file CAQuestData.xml in the main directory, which contains your profile settings!
If the database has been created properly, when you select an image from the directory structure you processed, CAQuest should show the right aperture value.