Cannot subscribe to iCal calendar

I'm trying to subscribe to a calendar but get the message that the calender doesn't seem to be in iCal format.

I tested the attached file with these validators:
http://icalvalid.cloudapp.net/
http://severinghaus.org/projects/icv/

and the calendar validates fine, funnily, the last validator makes use of iCal4j which is implemented in Team Calendars as well. Please see the attached log and ics file for more info.

Thanks a lot,
Peter