time-dependent problem, singularity error

Hi,

I am trying to solve a time dependent, multiphysics problem using "Transport of Diluted Species" and "Electric Current". In my model there are basically two electrodes inside water, and pulses are applied periodicaly. At every pulse, ion generation takes place due to water electrolysis, which I input as a reaction under the "Transport of Diluted Species". Also, another reaction applies everywhere in space and time in order to account for the water formation when the ions meet.

When I try to solve the problem, I am getting the error:
Repeated error test failures. May have reached a singularity.
Last time step is not converged.
-Feature: Time-Dependent Solver1 (sol1/t1)
-Error: Repeated error test failures. May have reached a singularity

If I decrease the ion generation to 10^(-6), the program runs without a problem and gives me a reasonable result.
Nevertheless, these values are not real, and I need to change the parameters back to the original ones.

Has anybody else had a similar problem? Can you please help?

Thank you in advance,
Nancy