undefined value found_ problem when simulating a 3d semiconductor p-i-n diode

Undefined value found.
- Detail: Undefined value found in the equation residual vector.
There are 6 degrees of freedom giving NaN/Inf in the vector for the variable comp1.Ne.
at coordinates: (1.50753e-005,-1.71741e-006,6.92302e-006), (1.50386e-005,-1.75096e-006,7.12623e-006), (-2.24562e-006,-1.67269e-005,8.71766e-006), (-2.29989e-006,-1.69435e-005,8.72902e-006), (-6.43443e-006,1.48051e-005,7.24292e-006), ...
There are 6 degrees of freedom giving NaN/Inf in the vector for the variable comp1.Ph.
at coordinates: (1.50753e-005,-1.71741e-006,6.92302e-006), (1.50386e-005,-1.75096e-006,7.12623e-006), (-2.24562e-006,-1.67269e-005,8.71766e-006), (-2.29989e-006,-1.69435e-005,8.72902e-006), (-6.43443e-006,1.48051e-005,7.24292e-006), ...
- Feature: Stationary Solver 1 (sol1/s1)


I keep getting this error all the time, please help if you have encountered such an error and were able to solve it

thanks;
Azam Ibrahim