Perhaps for my own benefit, I post the following. Writing down (or typing) something usually helps me remember things, so hopefully this will serve as a reminder going forward. I do this once in a blue moon, and everytime I have to go hunt it down and then for some oddball reason, I promptly forget it, promising myself I won't.
Every once in a while, Internet Explorer (6.0 in my case) seems to forget to display controls (such as buttons and dropdowns) using the current Windows theme - that is, with the nice sleek edges, rounded corners, and mouseover behavior. I haven't nailed down what it is that is causing this behavior; I don't have any CSS styles that would otherwise alter the border-style of the elements or anything. However, there is a META tag that we can use to force the issue.
By simply adding the following tag to the <head> section of the page you can ensure that themes will be (or will NOT be) supported on the page:
<meta http-equiv=”MSThemeCompatible" content="yes">