supporting French Characters

I have a website that runs in multi-language English and French, the English version is fine but I have some problems with the French language pages.

On the actual website the accented characters work perfectly for example "refaçonnage d’une pièce détériorée, après analyse".

However, when we open in the CMS editor the above text then becomes "refaçonnage d’une pièce détériorée, après analyse".

How can we rectify this as the french manager looking after the site needs to amend it and at the moment it is almost unreadable in the edit view.

Colin.