User unable to apply background image

Greetings,

I've got some user who is unable to apply a background image, either custom or one of the choices available.

The user is able to choose one of the images, but when he presses "Apply", nothing happens, doesnt matter which screen or image he chooses, it just happens as if there wasn't pressing any button.

Does anyone know what might cause this?

Thanks!

Regards,

Joan Ruiz Ramis