While Internet Explorer 9 does a more efficient job than its predecessors of identifying troublesome add-ons, sometimes it will still refuse to load because of a weirdly-coded add-on. If that happens to you, you can start IE in stripped-down mode from the command line.
Just type the following command into the Windows search box to launch a bare-bones Internet Explorer:iexplore.exe -extoff
As well as being useful for troubleshooting, this could be handy if you want to launch a bare-bones browser for some quick, add-on-free checking. (And yes, under those circumstances using Chrome might make more sense, but different folks like different browsers.)