Error 'Resource Assignment level invalid'

Hi,

I have created Resource Master - P48310

Resource Assignment constant - P48301

Work order created in P17714

48/RL UDC exists for WM,WO and SV 

When I am trying to assign a resource (individual) to a work order from P48331 - Resource Assignment program, after selecting the WO and a Resource and click Assign Resource, I am getting an error 'Resource Assignment Level Invalid'

Can some one suggest to overcome this?

Regards,

Thirunavukkarasu