Class diagram to ERD generation problems


I have couple of issues:

I have a class diagram with about 100+ classes (goog portion of it are lookup classes)and is trying to generate ERD from it.
The generation seemed to be working fine and then all of sudden it stopped generating the new classes I have added.

Did anyone encounter similar problem?

I created another class diagram and simply dragged classes from my master class diagram and the generation of ERD does not seem to generate anything.

I perform the ERD generation by “right-clicking” to execute popup menu “Synchronize to Entity Relationship Digram”.
I am using v6.0.

I would appreciate if anyone could shed some light on this.