Here's the source code for the error page I get hung up on. Can anyone tell me what the problem is?

<!-- Database error in vBulletin Installer: Invalid SQL: CREATE TABLE session (
sessionid MEDIUMINT UNSIGNED AUTO_INCREMENT NOT NULL,
userid SMALLINT UNSIGNED NOT NULL,
ipaddress CHAR(20) NOT NULL,
lastactivity INT UNSIGNED NOT NULL,
location CHAR(250) NOT NULL,
PRIMARY KEY(sessionid)
)
mysql error: parse error near 'NOT NULL,
userid SMALLINT UNSIGNED NOT NULL,
ipaddress CHAR(20) NOT NULL,
' at line 2
mysql error number: 1064
Date: Friday 23rd of February 2001 02:22:49 PM
Script: /talk/admin/install.php3?step=4
Referer: [url]http://www.botcw.com/talk/admin/install.php3?step=3[/url]
-->
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<p>There seems to have been a slight problem with the database.
Please try again by pressing the refresh button in your browser.</p>An E-Mail has been dispatched to our <a href="mailto:">Technical Staff</a>, who you can also contact if the problem persists.</p><p>We apologise for any inconvenience.</p>