radiation pattern clalulation problem in IE3D

i am simulation a dipole antenna . all the things are going well but when i try to do the current distribution and pattern calculation the following messages is displayed...what is the problem?


The simulation was terminated abnormally with error code = -4
Error Message: There is inconsistency between the MeshCurrentArrayFreqSweep and the port and plane wave numbers.

Have u applied any planewave excitation during the simulation?