Filter out MS Word 'quotes' for RSS

Hi All, I've got a forum/blog system which is displaying correctly in the browser. However, I've also got an RSS feed that is created from the data entered. It seems that some of the users are copying and pasting from MS Word or other packages, and this means that strange quote marks (among others) are appearing, and breaking the RSS feed. Obviously I need to convert these on entry, or on output into RSS. Does anyone know of an easy way to do this, or is it a case of identifying each unusual character individually? I've been searching on Google for some advice on this, but not found anything so far... Thanks in advance, Kev