What tha? Today is the first time I've Heard Of, Seen, or Recieved this error... ever! 
- This project started on my Mac but something is awry with my Adobe/Mac setup so I did a minimal Adobe installation to my Win7 64bit PC laptop. (Pr CC, Pr CS6, & En CS6)
I just finished Building & Transcoding my project in En CS6 on my laptop.
I closed En and went to lunch. When I tried opening my project an hour later, I recieved the error. 
Trying to move project folders into a new En project structure prompted the same error. 
Rebuild: Media on External Harddrive 
1. New En projects started on Desktop (1 for DVD - 1 for Blu ray)
2. Import Ps Menu... restarted En... OK
3. Import Audios (.wav)... restarted En... OK
4. Import Videos (.m2v)... "Indexing"... "Pending"... restarted En... OK
5. Create New Timelines from Media... "Pending"... restarted En... OK
6. Add Text to Menu... restarted En... OK
7. Created Buttons from Text... restarted En... OK
8. Linked Buttons to Timelines... restarted En... OK
9. Routed DVD Operations... restarted En... OK
10. Building DVD... Fingers Crossed!
* I have lost way too many hours of work due to various Adobe related issues over the last couple of weeks. 
__________
DVD Authored Successful!
(only difference was that I did NOT store the project on the external HD with the media... external HD the problem?) 
Now, on the the Blu ray.