for those that might wonder -- one of doris' blogs was just reloading wp-login.php after putting the correct username and password.
The fix was to delete ALL the files out of all the wordpress directories - wp-admin/, wp-includes, and their subdirectories, and all the files except wp-config.php in the wordpress root.
I did this because Doris uses fantastico to do her upgrades and fantastico leaves tons of old stray wordpress files on Doris' web space, and shes had her blogs for a while.
( she only emails me when something isnt working :P )
Then I reuploaded a new set of 2.7 files.
No edits, no cookies to clear, no browser cache to empty (and yes I actually tried to login before doing anything), just files :)