Thanks rlange - I ran into this problem again today and changing the page name wasn't an option; clearing the cache didn't work, but clearing history did. NOTE FOR IE USERS: be sure to UNcheck 'Preserve Favorites website data in the delete history dialog; it didn't work until I did that.
Seems to me this is a browser bug. If a URL delivers a 'page not found' error, why does the browser repeat the error even when the page has been added and the URL is now valid?
Is there an issue with my HTTP response code as indicated in my first post? As I said, I changed it from '301' to '307', but it still seems to glitch.