I think I found the problem.
It seems that PM5 is interpreting the lens information differently than V4.6 and generating a different entry for the lens type {lt}. In particular, AF lenses the also have VR have changed. For example, "AF VR Zoom 16-85mm f/3.5-5.6G IF-ED" now is "VR Zoom 16-85mm f/3.5-5.6G IF-ED", and the "AF VR Zoom 24-120mm f/4G IF-ED" is now the "VR Zoom 24-120mm f/4G IF-ED". Since I didn't have the new codes in my file, PM simply returned the original {lt} bracketed by \. Adding the new {lt} entries in the file solved the problem.
I guess I'll need to check my lenses to see what PM5 uses for the {lt} and add the new entries to the code replacement file.
Mick