Message No F2125

Hi

I have copied account group 0001 and created account group Z001 i have kept partner usage fields optional

I have assigned number range which has been defined as internal where in I have not checked the External checkbox

But when i go to save my customer data it gives me error stating"Data is incomplete ,check" mesage no F2125 at the Partner Function Screen

I am able to determine where the problem is.Can u kindly guide me on this

Regards

Sunil Srinivasan