There have been problems with the Green Fox and Blue Fox styles for some reason. Maybe they named the images wrong or they're in the wrong folders.
Right click the buttons with missing text and click properties to find the path pointing to the images, then check that they match with the images on your server. If so, then you just need to create a new button with text and overwrite it. If not, you will have to create the buttons and add the code to your header template.