upgraded from 5.0 to 5.2, and when I was done, I couldn't ftp to the box, though I'd been able to before. Turns out my additions to /etc/shells (for my own login shell) had disappeared, and /etc/shells had been returned to a pristine, out of the box state. Had the process left behind a .rpmsave file, that'd be at least consistent with the rest of the changes that had happened -- as it is, though, rpm -qf /etc/shells disavows any knowledge of the file. Oops. Some upgrade script isn't checking to make sure things haven't changed...
I installed RH5.0, added a last line to /etc/shells of /bin/zsh. I upgraded from 5.0 to 5.2, and observed the /etc/shells was identical to the one I had made in RH5.0. Sorry, couldn't duplicate the problem.
*** This bug has been marked as a duplicate of 365 ***