Error using Polarization in Transient EM wave problems

Hello,

I cannot understand the reason for the following error.
The following simple 2D transient EM problem (temw) is solved with COMSOL 4.3:
a pulse enters a rectangular domain from left (boundary condition = scattering, plane wave) and proceeds towards right (BC = scattering).
Top and bottom of the rectangle are PEC.
If I use Relative Permittivity = 1 in the Electric Displacement Field of the Wave Equation box, the solution is correct.
If I use Remanent Electric Displacement = 0, the solution is (correctly) identical.
If I use Polarization = 0, the solution should be the same (in my opinion) but instead I get an error connected to the variable temw.epsilonrxx (Failed to evaluate variable Jacobian).

Any idea of the reason for that behavior?

Thanks,
Roberto