I have had this problem persistently since 2.5.1
After I upgrade, I still get the message in the yellow bar at the bottom of the dashboard reminding me to upgrade to the latest version, and also a reminder in the page footer as well.
I have read that this could be due to ghost accounts, rogue entries in the wp_options active_plugins field etc. but I've checked everything in phpmyadmin and can't see anything out of the ordinary. So why is it still asking me to upgrade?
Should I try deleting all my plugins? Or backing up my blog contents from the database, removing, and rebuilding the database?
Any help is greatly appreciated.