IPTC data disappearing

Hi all,
I can enter IPTC data in Photoshop and/or Bridge, and all appears
well. However, when I upload an image to microstock sites, the data
doesn't appear. I downloaded ACDsee to check if the data appear there,
and they don't.

When I enter data in Bridge, I enter it into the keywords, document
title and description fields. This appears in the IIM (legacy) and
IPTC core sections.

I'm puzzled! Any help would be much appreciated.

Richard