Details do not exist for document 07 and vendor 13500

Dear Friends:

Using J11B, I entered Internal Exc.Inv No:7 and pressed Enter. I am getting the error 'Details do not exist for document 7 and vendor'.

The following fields data are displayed in post Excise invocie.

Document year,Vendor,Excise Invoice no, Excise Invoice Date,Excise Group,Purchase Order,Material Document.

We are having another problem also, Post invoice menu button is grayed or is not functioning.

How to overcome the error?Please advise in detail.

Regards

MSReddy