File: htmlbox.js

case 85: // U
if (e.ctrlKey && !e.shiftKey) {
glob_ha[d.id].cmd("italic");
}
break;

CORRECTION: "italic" should be "underline"

File: htmlbox-min.js
break;case"underline":h+=addToolbarItem("button","underline","undelrine","u");

2nd instance "undelrine" should be "underline"