OK. At the very minimum you'll have to use the "Save metadata to file" command on the "Metadata" menu in LR on each image that you have changed and want other applications to see. Second, LR will not update any embedded metadata in your RAW files, so if you've told PM to read embedded metadata before sidecar XMP files and your RAW files have embedded metadata, PM still won't see your changes.
You'll have to do some testing and investigation to get to the bottom of this issue. I suggest starting out with some new images, set PM5 to only write XMP sidecar files, and to read XMP sidecar files first. Then make your changes in LR, update the files with the "Save metadata to file" command and then come back to PM5 and you should see your changes that you made in LR. If that test doesn't work then I'd have to see some sample files to investigate further. If the test does work then you can take some of your other images and make sure to strip any embedded metadata (you can revert your RAW files to their original state on the Tools menu.) then modify them with LR, write the metadata back and then view them with PM5. You should see your changes. If not then I'd need samples of those files to investigate further.
-Kirk
