Because Elastic Audio can be very demanding of system resource, you might get this message if you're using it a lot (on several tracks). The solution is to disable Elastic Audio on a track (once you've got it adjusted to your liking) and "commit" the elasticized audio.

To disable and commit Elastic Audio on a track:

1) From the track’s Elastic Audio Plug-in selector,
select "None – Disable Elastic Audio."

2) If the track had any Elastic Audio-based processing,
you are prompted to "Cancel," "Revert," or
"Commit."
Choosing "Commit" renders and commits any Elastic Audio
processing on the track, writes new files to disk, and disables Elastic Audio on the track.

Page 770 (and a few following pages) of the ProTools 8 References guide has a nice, more details explanation of this process.