I changed the font size in Menu Bars by adding CSS {font-size:1.1em;} and that fixed the problem. Default must be 1.2em, as that setting recreated the IE overflow problem.
Comparing results in Chrome, Firefox and IE, I now see why I was getting different results in different browsers. It wasn’t screen size on my Windows 7 system’s 25-inch and 20-inch monitors. Each browser displays small-caps differently. In IE, the letters are larger and within words there’s little difference in size between the first and following letters. In Chrome, the letters are smaller and the first letter is significantly larger than the others. I’ve been developing pages in Chrome and should have been checking results in other browsers.
Thank you for your help.