Shipping point determination

Hi,

Here after creating Sale order,i found the shipping point is nit there in SO.This is due to wrong shipping condition maintained in Customer master.Then i have corrected the shipping condition ,and when i m going to change the current sale order,again there is an error showing shipping/Receiving point missing.Then i have check the OVL2 for Shipping point determination ,i found correct data maintained in it with combination of loading grp - shipping point condition-plant.Why this error appears?