IE9 And Swffit.js - Vertical Scrollbar In The Window?

I'm using Miller Medeiros' swffit.js script (swffit - Smart Flash Resize Script - 100% Width and 100% Height) to resize a Flash presentation. It's misbehaving slightly in IE9, and while I can overcome that with an "X-UA-Compatible" meta tag, I'd rather not introduce hacks to accommodate a current browser.For context, here's where everything ends up: Vertical Scrollbar. Click the first thumbnail. Use the little drag handle at lower right to resize the window. This works perfectly in FF3, FF4, Chrome, IE7, and IE8. But in IE9, I end up with a vertical scrollbar in the window.

In that context, there are a lot of "actors" involved, including the Highslide JS expander and the JW Player. But we can eliminate those red herrings. Here's a very stripped-down example, one that involves only swfobject.js, swffit.js, a few lines of HTML, and a boring little SWF file: SWF Fit Minimal. Change the browser window size, and you'll see that in IE9, the vertical scrollbar never goes away, unlike the result in any other browser. For this example, I'm using the swffit.js source code rather than the packed version, to make tinkering easier. The last non-beta version of swffit.js, by the way, has exactly the same problem.My guess is that there's something different about the way IE9 reports the viewport size, or about the way it responds to the resized Flash object, but I don't know how to track down those differences.