Conversion to MOBI not picking up Unicode

Hello

I'm new to calibre and ever so glad that I found it. Alas, I have one little problem. When I convert HTML generated from MS Word to EPUB format, all goes well. However, when I convert the same source to MOBI format, all the Unicode characters in the source are converted to ASCII. (So a prime character becomes the cents character, for example.) I have checked the Look and Feel options and the "Transliterate unicode characters to ASCII" option is not selected. And yet ny Unicode characters are doing just that.

Can anyone help, please.

Thanks

Geoffrey Marnell
Melbourne, Australia