Supersession problem

Hi All,

In material determination process we have 2 process

case 1) simple material determination: in this case system directly replace the material with other one.there is no other line item appear in sales order.

case 2) In second case system replace the material with other one & line item appear along with original material(means with superseded materiel appear with old material).

In both cases if material is not available on current date system automatic proposed the future date & material is confirm on that date only.

This process was happening in SAP 4.6 version.

Now system is upgraded with SAP ECC 6.0.

In new version simple material determination is running properly and system taking future schedule line date also(Case 1).

But in superseded material system is not confirming schedule line date for future delivery.

once we are saving the sales order schedule line is appearing in gray mode so we cant edit also.

for alternative now, we are just delete the line item & again put new item & we confirm the material.

I am not able to diagnosis this issue, kindly give me the solution..

thanks in advance

regrads

ajit