Timeline vs Theme and IE7

I've got 2 timelines in place on a site I'm building. Sadly, IE7 is the browser most people will use to look at the site. In my old site theme, built using Artisteer if that matters, both timelines display fine in these browsers: IE7 and 8, FF, Chrome, and Safari. I've recently implemented a new theme, also built with Artisteer, and suddenly one timeline will not show up in IE7. The page shows up, there is apparently a box created to hold the timeline, and I even see the vertically printed 'Timeline (c) SIMILE' image in the lower band. But there's no content, no upper and lower bands, and when you mouse over the area, the pointer changes to a text highlighter icon (like ][ but a single vertical line) rather than the 4-arrow click-dragger icon. As Admin, the 'Edit Clone Export' links also show up when you mouse over it. So it seems to be creating the area, but it's just not showing everything.

Again, this only happens when using IE7 (or IE8 in IE7 compat mode) and only in this new theme for one timeline. I've compared the source code of the page, and while there are some differences from page.tpl.php, and the CSS is slightly different, it's nothing I can see that would cause a problem like this. No errors in the logs, either. I'm thinking it must be a CSS issue, but can't see anything that would make it be invisible. Anyone have an idea of how to diagnose this?