I did a lot of googling, could see that this issue has come up before and tried everything, including the suggestions here:
In short, I've tried deactivating all plugins, switching to the default theme, adding lines to the .htaccess and php.ini files and I still can't add more. I'm wondering if things have gotten tangled up in the wp-options table? I seemed to be adding things fine initially, then I deleted what I had, started over, and since then I can only add a few pages to the menu and it keeps kicking me out to the home page instead of saving.
Could there be a way of cleaning up any entries concerning this in the database and seeing if that might help? If so, what tables would be holding this?