[AccessD] Combo-box control tip

I added some control-tip text to several combo-boxes, but the text
doesn't appear no matter how long I linger there the controltip does not
appear. I've copied the text into the status bar so I can fake it for
now, but I'd much rather have the control tip working. What am I doing
wrong? I assume that since control tip is supported in the properties
window that it actually works. Naïve?

Arthur