Steps to reproduce :
1 - open product window and make a right click on 'Comment/Help' field. Choose 'Editor'. The ok and cancel buttons are here ; it's ok !
2 - now open a new window or select another window.
3 - come back on the product window ; toolbar is missing ! you can't close the panel.
You have to click outside the editor to make them appear again (Note that this tip works only if the HTML editor is selected ; if you're on the 'Text', it won't works.