@michaelh, I have reconfirmed that the Page slug line does not appear until after publishing the page, and then returning via manage/edit page.
I tested on a clean install, no plugins, default theme, with a new mysql database on a 1and1.com server.
As before, the Post plugin line appears as expected.
This does not work with either IE7 or Firefox.
This does not work on two different pc’s.
This does not work on my local WAMP server or the 1and1.com server.
For me it’s a minor inconvenience; yet I’m curious what may be my problem.