Fatal Error, please help> Upgrading w/ One Click install

I was careless and went through the one click upgrade through my web host. I did not realize that you have to deactivate any plugins before installing 2.5 and now i’m receiving the following error when attempting to login into dashboard

Fatal error: Call to undefined function wp_register_sidebar_widget() in /home/.elba/brandongross/digishooter.com/wp-admin/includes/dashboard.php on line 31

I see there are many people experiencing similar issues, but since I tried upgrading through one click install, I’m not sure if I should be deleting files and attempting to reinstall (my host won’t allow me to reinstall since it lists it as already being upgraded)

help is appreciated!