Outlook ICS iCal BYDAY attribute giving "not a valid internet calendar file"

I have an ICS file like so:

BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:REQUEST
PRODID:Absorb LMS
BEGIN:VEVENT
CREATED;TZID=Mountain Standard Time:20110713T142655
DESCRIPTION:\n
DTEND;TZID=Mountain Standard Time:2011开发者_StackOverflow社区0728T130000
DTSTAMP;TZID=Mountain Standard Time:20110727T154733
DTSTART;TZID=Mountain Standard Time:20110728T120000
ORGANIZER;CN=ABSORB:MAILTO:info@absorbtraining.com
RRULE:FREQ=DAILY;UNTIL=20111223T000000;BYDAY=MO,TH
SEQUENCE:20241
SUMMARY:_blah's Test
UID:63118
BEGIN:VALARM
ACTION:Display
DESCRIPTION:Absorb Reminder
TRIGGER:-PT1H
END:VALARM
END:VEVENT
BEGIN:VTIMEZONE
TZID:Mountain Standard Time
BEGIN:STANDARD
DTSTART;TZID=;VALUE=DATE:20100101
RRULE:FREQ=YEARLY;BYDAY=1SU;BYHOUR=2;BYMINUTE=0;BYMONTH=11
TZNAME:Mountain Standard Time
TZOFFSETFROM:-0600
TZOFFSETTO:-0700
END:STANDARD
BEGIN:DAYLIGHT
DTSTART;TZID=;VALUE=DATE:20100101
RRULE:FREQ=YEARLY;BYDAY=2SU;BYHOUR=2;BYMINUTE=0;BYMONTH=3
TZNAME:Mountain Daylight Time
TZOFFSETFROM:-0700
TZOFFSETTO:-0600
END:DAYLIGHT
END:VTIMEZONE
END:VCALENDAR

This doesn't work when you open it in Outlook 2010 (you get not valid internet calendar file message and it is NOT helpful). However, if you change the line 13 to:

RRULE:FREQ=DAILY;UNTIL=20111223T000000;BYDAY=MO,TH

or

RRULE:FREQ=DAILY;UNTIL=20111223T000000;BYDAY=MO,TH,FR

It works.

All of these variations pass the iCal verification tests, it's just a stupid issue with outlook. Does anyone know any work-arounds or something else I can do?

Cheers, Rich

Change the method to publish and try... I guess it'll work

METHOD:PUBLISH