just a guess -- I've seen "smart quotes" do this to a couple of different applications, not necessarily Fox. I think the offending ASCII values are 147 and 148, but there are a few other culprits anyway.
You can try chrtran()'ing for all the ones you know about, making reasonable substitutions, and add to the strings as you find out about them.
Something like this:
#DEFINE EDS_TEXT_BADCHARS CHR(145)+CHR(146)+ ;
CHR(147)+CHR(148) + ;
CHR(0)+CHR(26)
#DEFINE EDS_TEXT_CHRTRANS "''" + ;
[""] + ;
SPACE(2)
lcValue = CHRTRAN(lcValue,EDS_TEXT_BADCHARS,EDS_TEXT_CHRTRANS)
REPLACE Whatever WITH lcValue