checklink: [Fwd: link checker error]

Error is at:
http://validator.w3.org/checklink?uri=http%3A%2F%2Fwww.columbia.edu%2Facis%2Fnetworks%2Fadvanced%2Fnew-index.html&hide_type=all&depth=&cookie=nochanges&check=Check

-----Forwarded Message-----
From: Daniel Medina
Subject: link checker error
Date: Tue, 01 Jun 2004 15:42:02 -0400

Processing http://www.columbia.edu/acis/networks/advanced/new-index.html
Software error:

Can't call method "canonical" on an undefined value at 
/usr/local/validator/httpd/cgi-bin/checklink.pl line 608.

For help, please send mail to the webmaster (web-human@w3.org), giving 
this error message and the time and date of the error. 

$ date
Tue Jun  1 15:41:42 EDT 2004