3.0 Update Gave Fatal Error

Hi, I hope someone can help me with this:

On the dashboard of my admin page, I clicked on the “Update to 3.0” link and it downloaded it like it normally does when you download anything, and it said it was successfully downloaded. However, when I went to my website, and tried to go back to my admin/dashboard, it gives this error:

Fatal error: Call to a member function add_rewrite_tag() on a non-object in /home/content/91/5308191/html/wp-includes/taxonomy.php on line 289

I don’t know what to do because I have very little coding skills, and I can’t even log into the dashboard anymore. My files are hosted under godaddy.com, and I’m assuming that I need to fix something in the taxonomy.php file, but I’m not sure what. If you can help me it would be greatly appreciated.

Thanks!