Welcome to the forum.
Do you have Apple's QT Player installed, and if so, what version?
Did you install the Additional Functional Content, which includes Themes/Instant Movies, Titles and DVD Templates?
I had QT version 7.6.9. Your answer prompted me to check for upgrades. Upgrading to 7.7.1 failed so I uninstalled 7.6.9 and installed 7.7.1 manually (after having to manually delete a file left behind by 7.6.9 uninstall - 'error getting file security' message ).
Instant movie now works fine.
BTW - I had recently installed the Additional Function Content &, on checking again, my 'D' drive is in fact my DVD drive. There may have been a pointer to there from my recent installation of the Additional Function Content.
Thank you for your time.
Thanks for taking the suggestion one more level, especially when you had to do a manual uninstall/reinstall to get it, and then for reporting success.
Good luck, and happy editing,