I'd just like to interject for a moment. What you're referring to as Windows 7 is actually Windows Vista service pack 3, or as I've recently taken to calling it,
Windows Mojave 2.0.
Seriously, Vista was fine security-wise. The only problems were fixed after the first service pack, and those were mostly related to drivers (most of which were based on the outdated XP driver model instead of the completely redesigned one that Vista and 7 use). Vista is a pleasure to use these days, I use it and 7 on many of my systems and there are few discernible differences.
Internet Explorer 9 is not out yet. I haven't heard of this sort of problem, normally IE8 works great on Windows Vista and Windows 7. If Firefox works, use it for now, but if you see a fix somewhere, I'd recommend trying it out.