Arbortext Editor compiles document types, .dtd files.
3 files are created, .ptd, .pro and .dec.
Often an upgrade requires these files to be re-generated.
(Date stamps change, a minor change in the handling of .dtd functionality, 32-bit vs. 64-bit, etc.)
As the error message states, the .dtd file needs to be re-compiled, and the .ptd, .pro and .dec files need to be re-generated. Re-compilation probably needs to be done all your .dtd files.