"Age group could not be determined" i am unable to save Insurance plan

I've done all plans. when I tried to create 168 - Insurance Plans, I got the following error.

"Age group could not be determined"

This happened after I entered Benefit Plan and Insurance Option in Plan Data tab. The system would automatically take me to Insurance Coverage tab and highlight Calculation Date field where the system is automatically taking today's date.

I am unable to access Beneficiaries tab also.

What could be the mistake. Please help!!!

Thanks,