Only small part of video on Blu-Ray

[jpjdenmark]

Just got a Casablanca Karat and made my first HD projekt. I made a SD version and burned it on DVD, no problem. Then I changed to HD, and inserted a blank blu-ray disc (Verbatim, BD-R 6x). After rendering, the machine burned the disc.The project is two movies, a short movie (4 mins.) and a longger (30 mins.) The result is depressing: The menu is very jerky, the short movie plays perfect, but the longer stops efter 4 minutes. Tried again - and again - same result - now I have 4 BD-R discs, where the movie stops after 4 minutes. When I try to verify the disc, the Karat informes me, that there was an error. Yes, I guessed that - but what? - why? - and what is my next move??