carlfogel,
Thanks for the link, it eventually helped me find the answer.
An installed program had disabled Win7 aero. Some investigation revealed that a "mirror driver" was interfering, and it was LogMeIn that was the culprit. I uninstalled LogMeIn then deleted the mirror driver that it had installed for the display adapter, and aero is back, with the page previews.
I know that there are many who use LogMeIn, anyone else seen this?
