Assign item category to GL account in ecc 2005

Hi

We are using ECC 2005 version, With New GL functionality.

I think i am missing some thing in the Configuration part.

When i am posting an Vendor invoice Its giving an

Error Message : "Assign item category to GL account in ecc 2005"

Looking forward for your suggestion in this regard, how to fix this.

Regards,

Kalyan