I noticed this with 8.5.2 and recognized the symptom from my days of messing about with some of the "IBM only" design elements in ND7 (there are a few, seemingly innocuous but obviously different implementations of standard elements in the mail template tinker with can screw your install up royal).
After noticing, I thought I'd better just download the 8.5.3 client. Wow, that experience took me back in time about 8 years. IBM's website is still horribly organized and byzantine. It's amazing to me that they can't get their act together and make a website that has a consistent, simple and easy to use interface. Sort of explains a lot about the current state of the designer client I suppose.