Oops, I assumed that you still had a Moodle 1.3 installation which refused to update to a Moodle 1.5.2 installation because of this problem with the wiki.
Since then an extra security measure was added to the code. You may get an error message A required parameter (sesskey) was missing
when you follow the directions in my earlier post.
If that is the case you can still manually delete the wiki module by typing the following http://www.beachcollege.net/m/admin/modules.php?delete=wiki&sesskey=S2oQpcIG7x
The problem is: the bold code changes everytime you login. You need to figure out which one that is for your current login session.
To do this:
(still logged in as admin) visit a course
Turn editing on
hover your mouse over one of the edit buttons next to the activities
in your browser's statusbar you should see a link which include s a part
&sesskey=S2oQpcIB7xWrite down the characters of the sesskey code
Visit
http://www.beachcollege.net/m/admin/modules.php?delete=wiki&sesskey=S2oQpcIG7x but replace the bold sesskey code in these instructions with your own sesskey code.
Hope this saves you a complete Moodle reinstall. And yes, it is still possible to reinstall the wiki module. In fact this trick will only delete the wiki databases (the ones that seem to cause this problem) not the wiki code. If you visit your admin/index.php afterwards, it will reinstall the database tables again, hopefully succeeding this time.