This will be fixed in the next build.
Let me add a little clarification here: Most internet-explorer-9 bug reports here on meta currently have a status-declined tag, and this has been interpreted by some to mean "Shut up, we don't give a §$%&."
But of course IE9 will be considered a supported browser once it comes out, and we will revisit (and, as you see here, have already started revisiting) all these bug reports.
Chances are that some of these bugs are still around when IE9 comes out. This particular case, for example, was a jQuery plugin that failed badly at user agent sniffing, so this was indeed not an IE9 bug; just another proof that user agent sniffing is at best dangerous (even if, unfortunately, not always avoidable).
What we want to make clear with that tag is the following: Currently, using IE9 (or Chrome 10, or Firefox 4) is considered unsupported, so these bugs have a low priority for us. Making the sites work in released browsers comes first. If you're using a pre-release browser, expect some weirdnesses.
But we still appreciate that users are testing our sites in these browsers and make us aware of potential problems in advance. And you can be sure that sooner or later, most internet-explorer-9 bugs will be either status-completed or status-norepro.