I've searched the support forums, and no one seems to have quite the same problem as I do.
I've just moved a working WordPress blog to an existing directory following the steps in the Codex, so I can use a specific URL address for the site. I get this error when I load my site:
Fatal error: "Call to undefined function: get_header() in .../index.php on line 5". Can anyone please help with this issue? Thanks!