Fatal error: get_header_image()

Suddenly, today, after posting a new message, I started getting this error in my wp-admin side of the site:

Fatal error:
Cannot redeclare get_header_image() in /home/rtatum/public_html/blog/wp-includes/theme.php
on line 491

Now I cannot access my wp-admin.

Nothing changed. I just did a directory comparison with my local copy of the files vs. the version on the site, everything is identical. I’ve optimized my database. I’ve no clue what’s going on.

Help?

Rich
rich [dot] tatum (at) tatumweb [dot] com