That aren't text boxes, but special selectors that open a pop-up when clicked where you can select your choice. These selectors work with JavaScript, so make sure you do not block JavaScript.

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (e.g. Adblock Plus, NoScript, Flash Block, Ghostery) then make sure such extensions do not block content. There is security software that can interfere with loading content, so check that as well.

Thanks for this. JavaScript was not the problem - the extension "Browsing protection by F-Secure" must be be disabled for the "special selectors" to function correctly.