I've noticed the same problem.
My config is:
$wgWhitelistEdit = true; # true = user must login to edit.
$wgWhitelistRead = false;
$wgWhitelistAccount = array ( "user" => 0, "sysop" => 1,
"developer" => 1 );
In fact it seemed to be working until I used the Sysop account to create
a user (using the Special:Userlogin page).
From that point on, it was impossible to login, I would
systematically get:
Sysop access required
The action you have requested can only be performed by users with
"sysop" status