Thank you for the hints.
I went off to the AMD ATI Drivers and Software site (http://ati.amd.com/support/driver.html
) and got the latest version of their Automatic Installer packages (turn out I had version 8.29.6 and the new version is 8.34.8; just seemed like a good idea to use the latest and greatest). It's amazing what will come flooding back with just the smallest hint...
Anyway, uninstalled the 8.29.6 drivers (per instructions), installed 8.34.8 drivers (per instructions), all is well with the world. GoogleEarth starts smoothly, videos play at the proper speed, fgl_glxgears spins like a mad rabbit.
Thanks to all.