I must admit, I'd never noticed the OK|Cancel at the bottom. After a bit more experimenting I realise that it's only a problem if I go straight from editing a note to saving the file. Clicking anywhere else has the same effect as clicking OK. So to be more specific, the problem can be reproduced as follows:
Open project, Edit note (without clicking OK or Cancel), File Save, Close Cakewalk
Any changes in the edit are then lost.
AMB