fckeditor in older oscommerce - some IE versions dont show

Hi,

There is FCK in an older oscommerce site and it shows in FF and in some IE browsers, but not in other version of IE. Seems really random.

I think I should upgrade it to the latest stable FCK but am not sure which one and what files need updating.

Is it just a matter of changing the fckeditor.js file or are there others which ned changing.

Thanks

oz