Hello,

Finally the first problem was solved.
(interrupt VS bulk out)
It was a bug in my code.

The problem was that I was clearing the interrupt pending flag this way
FIFLG|=ENDPOINT_3_MASK;
But those interrupt bits are cleared when firmware writes '1' to it, so I was also clearing all other interrupt flags...
The right way is: FIFLG=ENDPOINT_3_MASK;

It is just several months since I started programing firmware so I guess this is a newbie mistake.

Xavi