It happens very often when I do an updated of my Inventor model.
Unfortunately, you must open the latest valid version for your file saved in the directory Oldversions.
To do this you must first install SP2.
it doesnt seem like there is a directory OldVersions for Inventor Publisher (.ipb files), only Professional. changing the version of the assembly I have, wont be updated or even recognized in publisher because I cant even open the file in publiser