Just a couple of general points that may help in future.
Unless a file has the Podcast flag set, audio files imported into iTunes will be treated as Music (apart from m4b audiobooks) and video files as Movies. You need to manually change the Media Kind after import.
As well as "Media Kind" there is another property inside iTunes called "Video Kind" which indicates if a file is a Movie, TV Show or Music Video. Current builds of iTunes *do not* alter this value in tandem with a change in Media Kind. This could potentially cause problems with smart playlists and perhaps even remote access to the library. The Video Kind property can be set from script.
Given that Media Kind is an internal property of the iTunes database there is no good reason that it can't be applied to any file whether locked or not, but I suspect iTunes first checks for write permissions before making changes so permissions may be an issue whenever you are unable to change the Media Kind.
Unless your selected audiobook files are all in .m4b format iTunes will report any selection of two or more audiobook files as being
Music. Ignore it. It can't handle mixed property values either, e.g. a mix of compilation and non-compilation tracks will always show as *Part of a compilation: No.*
When working with single audiobook files you cannot change the status of the *Remember playback position* and *Skip when shuffling* flags. Simply select more than one file to adjust.
For more tips on audiobook organisation see
http://samsoft.org.uk/iTunes/audiobooks.asp
tt2