Adminp "Document is not signed Error" when processing Change HTTP Password request

Dear all,

I get the following message: in Administration request db.

Admin Process: Received the following error

Change HTTP Password in Domino Directory

Databases processed: None

Errors: Title: Administration Requests (6) Path: admin4.nsf; Error: Document is not signed.

This error occurred only on all mail dbs other than on Administration server.

Can some body please help me.