I found the quickest way to resolve this was to convert all of my existing WMF file into the PICT file format.  Using one of my Linux servers I ran the following shell command against my picture library:

find /home/user/clipart/ *.WMF -print0 | while IFS= read -rd $'\0' f;
do echo "[$f]";
convert "$f" "$f.pict";
rm -f "$f";
done

This creates a list of files who’s file-name ends with WMF.  We then loop through each of these file-names converting each and saving it with a .pict file extension.  The IFS= read -rd parameters are absolutely necessary should your WMF files contain spaces.