Hi Steven thanks for the reply. I know what's going on now. It's the irritating issue that JB will not add captions to images that have been re-saved. Thus in my workflow I shoot raw and process them through ACR and they are outputted as j-pegs. If I use these jpegs immediately to create a JB gallery then the IPTC is pulled in, if I do further adjustments and re-save them then the IPTC won't be pulled into JB.
This is a significant problem. Clearly I wish to present galleries to clients with caption info AND images looking as good as they can, but there's only so much you can do in ACR with other critical adjustments only possible in Photoshop itself. I wonder if this can be fixed in later versions of JB? I certainly hope so.
I know you can manually cut and paste caption info but this is much too time consuming and simply not viable with large galleries.