I have done this now, right click, properties, compatibility, ticked "run this program as admin".
When I open the program it prompts me to confirm run as admin and I say yes.
Then I open the project, and try to export, the same prompt "Processing Sound Clips" appears, it does not go away (its been 5 mins)
Previously the export has taken much less time (its only 2min video)
Any other ideas?