Does anyone have any expertise with .ICS files?

This file is created from an automatic script, and something about it is wrong and I'm not sure what:
http://www.martian.at/calendar/VixyAndTony.ics

Google Calendar chokes on it when I tell it to "add by URL", I get "Warning: did not successfully merge all events" from Google. But it passes validation when I feed its URL to this web site:
http://severinghaus.org/projects/icv/

Can anyone tell what's going wrong here?