After completing the main story I purchased 3 DLC's at Steam - Dead Money, Honest Hearts and Odd World Blues - and while Honest Hearts is running without a problem, everytime I try to start Dead Money and Odd World Blues it ends up with "Falloutnv has stopped running" message.

I've tried many things I found here on the forum, but with no success:
- removed my companions
- removed all the items
- quicksaved / quickloaded before entering DLC
- verified integrity

Any other ideas ?

I have no mods installed, running the game with Win 7 Pro 64-bit, Core i7-2600, 12GB RAM and GTX 560 Ti graphics ...

have you tried reinstalling owb by deleting its files and validating the game files??