I'm STILL trying to figure out the problem here. I've noticed a few other programs having trouble opening. Mass Effect 2 gives me some error about a "side-by-side configuration" problem, Dragon Age Origins can't find "fmod_event.dll," The Witcher randomly doesn't work and neither does Oblivion (and that's my favorite game!!!). Sine multiple programs give me the same error (the side-by-side config one I get with both ME2 and QuickTime), I think this is a Microsoft problem, not an Apple/iTunes problem. I'm in contact with somebody at MS support but the dude is taking forever to respond, hopefully because he's hard at work looking for a fix.
I'm wondering if we're all having the same Windows Update problem. Mine keeps telling me I need to install a security update for MS Visual C++ 2005 sp1 (KB2538242) but when I do, it lists it as an important needed update again no matter what. I've reset WU, cleared the "cache" or whatever it's called in this case and uninstalled/installed the update multiple times, nothing gets rid of it.
Does this stuff sound like what you guys have also been dealing with or is your problem exclusive to iTunes/QuickTime? I'm wondering if they're related. The MS guy swears it's an Apple issue with iTunes (naturally, anything to avoid helping) but this all happening at the same time seems a bit too conspicuous to me. Strongly considering just giving up and reinstalling Windows.
I did find a slight work around to at least get media onto my iPod. A free program called Floola is pretty basic but works for the time being.
Anyway, let me know if your guys' problems are like mine and maybe we can try figuring this out ourselves since neither MS or Apple seems to care.
PS (I know its long, sorry) I tried Kent102's solution and it didn't work for me but I read on another thread that it resolved the Mass Effect 2 issue I mentioned earlier for somebody else so try that out, I'd think it's your best bet at this point.