php nuke fatal error: Call to a member function on a non-object

Hi. Im still trying to get my PHP nuke running. I've got a mysql
server set up, and i used nuke.sql to get all of the tables populated.
Now, my install guide (at www.nukeresources.com ) says to go to
(yoursite)/index.php

Now, when I go there, all I see is a bunch of source code and then an
error message at the bottom. it reads:

Fatal error: Call to a member function on a non-object in d:\program
files\apache group\apache\htdocs\nuke\html\mainfile.php on line 86

I just cant figure it out. the lines which produce the error are:

84 $mainfile = 1;
85 $sql = "SELECT sitename, nukeurl, site_logo, slogan, startdate,
adminmail, anonpost, Default_Theme, foot1, foot2, foot3, commentlimit,
anonymous, minpass, pollcomm, articlecomm, broadcast_msg,
my_headlines, top, storyhome, user_news, oldnum, ultramode, banners,
backend_title, backend_language, language, locale, multilingual,
useflags, notify, notify_email, notify_subject, notify_message,
notify_from, footermsgtxt, email_send, attachmentdir, attachments,
attachments_view, download_dir, defaultpopserver, singleaccount,
singleaccountname, numaccounts, imgpath, filter_forward, moderate,
admingraphic, httpref, httprefmax, CensorMode, CensorReplace,
copyright, Version_Num FROM ".$prefix."_config";
86 $result = $db->sql_query($sql);
87 $row = $db->sql_fetchrow($result);