item category not defined for the material error

Hi friends,

We have a scenario where we enter a material which should be as text material.For this we have cretaed a material which has item category as NORM. and we have also maintained the item category assignment

ZSO1 NORM TAN ZOWN ZHIR ZADD

ZSO1 NORM TEXT TATX

Still when we create a sales order we are getting the error as "Item category TATX is not defined for this item"

when we see the F4 help we see only TAN,ZOWN,ZHIR,ZADD,TAW & DSI.we dont know froem where the item categories TAW & DSI are determined.

we require the TATX item catergory to be determined.

Please suggest

AJ