It just happens with the one file? You might try:
Next up, try trashing preferences:
Thanks for your quick response. Some more observations:
1. It happens with several files.
2. Once it starts happening, I can't get the Preferences Dialog to appear either, so something is blocking all dialogs
3. It doesn't happen with a blank document, but if I take content from an affected document and paste it into a blank document, the problem shows up again.
4. If it starts happening, I can clear all the document content, and it will still happen.
I've already trashed the preferences but the pattern remains unchanged.
What operating system are you on?
Win 7x64 Pro with plenty of power! Exporting was working OK a couple of weeks ago.
Could the windows be hiding behind other windows? Are you locked up until you press Escape or can you work normally after opening Export or Prefs?
Do you (did you) ever use a 2nd display?
I discovered the problem. It was a dodgy Indesign CS6 plugin that was installed along with High Logic Maintype font management software. For some reason, this was causing the problem. I have removed the plugin and normal operation has resumed.
Confirmed by this thread on the vendor website: Adobe Indesign CS6 Plugin "crashes" - Font Forum
Thanks for your help!
Good for you for finding this on your own, and thank you for coming back to let us know.