REWORK ORDER COSTING

hi all

i've created a rework order using co07 for a qty of 20 and assigned a reference op set, distribution rule for order settlement to parent order.But,when i attempted to calculate the order costs, the system displays an error , saying Object was not costed ,Message no. CK060.i've maintained control key relevent to costing in the work centre and activity types.

any help much appreciated !

cheers

sasi