CSS help needed — quick!

[Update: Resolved. See comments.]

Something’s gone wrong. In fact, it may have been wrong for a while. Some of this site’s CSS isn’t working properly in Internet Explorer.

Here’s what I see in Firefox (click to enlarge if you like):

But here’s what it looks like in Internet Explorer:

For some reason the boxes on the home page aren’t appearing in IE, nor is the text within those boxes being formatted correctly.

CSS users, help!

The full CSS file is here. Here’s what I think are the relevant snippets:

This creates the box:

.box
    {
    border: 1px solid black;
        font-size: 100%;
    background-color: #cccccc;
    padding: 0 8px 4px 4px;
    margin: 0 0 6px 0;
}

And this formats any H3 tags within a box:

.box h3
    {
    font-family: Verdana, Arial, Helvetica, Helv, sans-serif;
    font-weight: bold;
    font-size: 16px;
    line-height: 14px;
    color: black;
    background-color: transparent;
    letter-spacing: -1px;
    margin-bottom: 4px;
    margin-top: 12px;
}

Any ideas why those boxes aren’t showing? And why the text inside isn’t being formatted the way I expect it to?

HELP!