At work, I am running Windows 7 (64-bit) on a Dell Optiplex 780 PC.
When Internet Explorer 9 was released, I installed the 64-bit version on this PC. Right from the start IE9 was unbearably slow, pages didn’t load, or only showed after you moved the mouse (it reminded me of a “peekaboo” bug). It would also hang after you simply had it running for a few minutes (without actually using it).
In short: IE9 was pretty much unusable on this system.
I tried to uninstall, then reinstall IE9, which didn’t help.
My next step was to reinstall Windows… until my colleague suggested to update my video driver.
My Dell Optiplex 780 is equipped with an “ATI Radeon HD 3400 Series” video card. I went to the ATI (now AMD) website, downloaded the latest driver, installed it, and…. IE9 runs flawlessly now!

I’m sure this has something to do with IE9′s hardware acceleration.
Conclusion: If IE9 is slow, or exposes generally weird behavior, try upgrading your video driver.
Please leave a comment if this article helped you. Thanks!