Failed to evaluate variable Jacobian

Hi
I simulate the rib waveguide with the sio2 substrate and material of the core Er:Ta2o5
i define the lambda=1550nm in global definition>parameters, and in the step 1:frequency domain:c_const/lambda
in the electromagnetic wave field i define 2 port for the core(Er:Ta2o5):
port 1:port type :rectangular and wave excitation is on
port 2: port type :rectangular and wave excitation is off
mode type is TE,mode number :10

when i want to simulate,i am getting the following error:

Failed to evaluate variable Jacobian.
- Variable: mod1.emw.tE0modex_2
- Geometry: 1
- Boundary: 7
do you know how to fix this problem?
Thanks in advance for the comments

Michael