Kirk,
When editing keywords in the IPTC info panel the keywords don't always get displayed correctly when switching to the next or previous image.
Workflow: I add common keywords through the Keywords panel (Cmd-K). When done, I open the IPTC info panel (the one you get when you press 'i' on an image) and add keywords that are different for every image. While the cursor is still in the keywords field I click with my mouse on the "Save & ->" button. In more than 50% of the cases I see the new image with the correct caption but the keywords of the previous image are still in the keywords field. Tabbing out of the keywords field and back in solves the problem.
Using PM 4.5.2 on Intel OS X 10.4.10