Yes and no. It's a problem with IE alright, but Microsoft has no interest in creating a patch to make it work with QT. They seem to have an agenda with their own video format. Nonetheless, quicktime has taken it upon themselves to create some sort of patch. The problem is, I'm not exactly sure how to find it.
Here's what I do know: When I went to the QT website for a clean download & install, the task seemed to be more or less automated. I didn't have to download a specific installer file to my hard drive and then launch the program; The entire process was taken care of automatically. At one point in the process it prompted me about the special IE patch, and then automatically installed it. If you did not see this specific prompt, my only guess is that it assumes, based on your settings, that you already have the patch.
If this be the case, you can probably get around the problem by completely uninstalling QT and all of its related components before reinstalling. It sounds like a long-shot, but if that's really the problem, it should work. If that's not the problem, then I'm still in the dark and we need to just keep poking around the apple website for possible solutions.
Jonathan