I am getting exactly the same warning or error, but I am using XFA Dynamic Form which Signature Locking feature.
I am using Adobe LC Desinger ES2 + SP2, and Adobe Acrobat Pro 9.1.
After the document is signed I get this message:
Signed and all signatures are valid but with unsigned changes after the last signature.
Then after I close and open the PDF, I get message that the last signature was invalid "At least one signature is invalid".
When I try to view the differences using document compare (2 pages only), the report says that page was moved or matching page was not found.
I have a feeling that this is a bug.
Any help will be appreciated.
Tarek.