[moved] Fatal error in ansoft hfss

While am simulating my antenna design in ANSOFT HFSS 14, i am getting FATAL ERROR message, If i click on that error then hfss is terminated. Can anyone give the solution to my problem.

Thanks in advance.....

Is it licensed copy? Did you check with Ansys?
Fatal error is typically related to memory.

Yes Sir, am using Licenced version of HFSS 14 version. But am not getting this type of problem previously. Can you tell me how can i avoid this problem.