Valuation Type problem

Hi!

I have maintained two valuation type for a material, when i am preparing the PO for that material with two line items, one line with valuation type and the other type without valuation type.

When i am doing GR one line item for which i assigned valuation type in PO it is grayed and the other line where i have not assigned any valuation type in PO is editable and the same valuation type of first line is appearing in GR even i have deleted and posted the document but both the lines having the same valuation type after posting the document.

Regards