Thanks for taking the time to check for me.
It does the same for the default view. Even stranger, I tried a fresh install, then the beta, then both again with a portable installation. Same results each time! If it's not doing it for you, it must be something it doesn't like about my system.
For the moment, I've set it to use an invisible font, although this leaves a transparent bar across the bottom of the images (as would be expected). Looks like I'll just have to live with it! Thanks for your advise all the same.