The most common symptom of this Apple FUBAR is that embedded movies from sites like YouTube will not display. Instead, users get a Quicktime logo with a question mark.
Some have suggested deleting the npqt*.dll files from your browser's plugin folder. But this doesn't always work.
Today I got pissed off enough to install and uninstall Quicktime several times while watching the registry for changes. Sure enough, the x-shockwave-flash MIME type was being hijacked by Quicktime.
To return your browser's .SWF preference to the Flash plugin:
Your browser should now use the Flash plugin instead of Quicktime.
You're welcome.
Tim Spencer
spencer@rock103.com