[Mediawiki-l] Mediawiki pages deleted after upgrade?

[Sullivan, James (NIH/CIT) [C]]

I just had a strange experience and was wondering whether anyone else
has run into this.  I have been upgrading various wikis from version
1.6.10 to 1.11.2 and moving their databases from a MySQL 4 DB to a MySQL
5.1 DB for the past month or so, and all seemed to be going well, but
yesterday, after an upgrade was complete, I tried to modify the
Mediawiki:Username page so it would display something other that the
"Log in / create account" message.  When I tried to edit this page (as
WikiSysop), I saw the following:

-"View or restore one deleted edit?" in small font with "deleted edit"
being a link to the deletion log.
-The following above the edit box: "You've followed a link to a page
that doesn't exist yet. To create the page, start typing in the box
below (see the help page for more info). If you are here by mistake,
just click your browser's back button."
-In the edit box is the text "Log in / create account".

When I edited this text and tried to save, the Preview came up showing
nothing in the preview area.  The Preview button does the same thing.
Its as though the wiki is acting as though the page does not exist while
showing me the text in the page.  I've tried other Mediawiki pages
(those on the Special:Allmessages page) and I get the same behavior

Now, when followed that deletion log link, it took me to the "View and
restore deleted pages" page where it showed a history log of the
"MediaWiki default" page.  I selected this page and hit the Restore
button. The "Mediawiki:Username" page is now able to be edited but not
other Mediawiki: pages.

So for some reason, it seems all Mediawiki: pages are marked as deleted.
Regular (Main:) pages are fine, and if I didn't need to modify the
Mediawiki:Userlogin page I never would have known anything was wrong.

My question is whether this is normal behavior in 1.11.2 or whether I
did something wrong during the upgrade.

Thanks in advance for any pointers.  Just a final note: Since the wiki
seems to be functioning well I'm living with this oddity, and if I need
to modify another Mediawiki: page, I'll just undelete it too.  But it
seems certain that something is not right with this wiki.

-Jim