Problem with piezoelectrics

Hello all,

I'm working on a silicon beam with a piezoelectric part on te top of it. I would like to obtain the normal modes of oscillation as well as the electrical voltage in the piezoelectric part... but I came across an error:

"Three factorizations in a row failed. Check the model. It is possible that the model contains the kinematic coupling definition set up in a way that a degree of freedom has neither mass nor stiffness."

There are no warnings at all and I was not able to find a proper solution.I would be really greatful if you could give me some advince, or provide me some kind of help.

Thanks in advance and sorry for my English,

Carlos.