Are you doing Code Replacement through the IPTC Stationery Pad? What kind of files are you captioning?
I try to caption JPG files extracted by PM from Canon EOS 1D mk2 RAW files.
I captioned the files in PM using either the stationary pad or the simple image IPTC editor. My replacement codes were put in the files before my replacement file was created. I edited the replacement file after I saw all codes I needed to set the caption for.
Code replacement happens fine after adding the replacement file list. But the replacement seems to be temporary. It is effective only in PM. Opening the allready replaced files in other application shows my codes instead of the replaced text. The same is true if I save the images as.