Joe B.
I haven't tested if the GISUser can edit a FC in a FGDB because that user only exists to connect to the SDE database and isn't a Windows Active Directory/Computer User. It would be my understanding, maybe incorrectly, that when a user is interacting with the FGDB they would not be connecting to it as the GISUser, but as their Windows user (Bubba). Bubba can do whatever they want to the FGDB as long as they have permissions to the directory (locally or network share). I would think that Bubba is writing the geocoded results into the FGDB, but is just using the GISUser to connect to the SDE database. I tested this theory by creating a GISUser account on my local machine and then giving it full permissions to the folder which contains the FGDB into which I'm writing data. No luck, still getting the same error message...
Also, I'm not aware of being able to set permissions on a FGDB or FC's within a FGDB. I poked around ArcCatalog and didn't see where it could be set. Am I missing something?
Thanks for the suggestions!