Greatest of thanks to the Ran Davidovitz blog for investigating and publishing about this confounding IE bug. removeChild in certain cases will cause a secured (https) page in IE to toss up the security warning about mixed content (which, on some pages I've been to, actually means "the ad banners on this page are susceptible to traffic sniffing by third parties! oh noes!").
Obviously, IE isn't the only browser that contains bugs, and its CSS rendering alone should be addressed first, but my teeth hurt a little from grinding over an obtrusive security warning from the browser about normal execution of code on the page.