How to subscribe an icloud calendar in google calendar

Hi everyone

A few menthes ago I had my iCloud calendar shared (I did it in iCal in my Mac OS X Mountain Lion) and subscribed in Google Calendar.

Some weeks ago this stopped working. So I canceled both sharing in iCal and subscription in Google Calendar and did it all again from scratch.

It doesn’t work. Google says "The file <file_name> is not a valid Internet Calendar file".

I tried also to do it at my job, in Outlook 2010 and the result is the same.

Any help?

Thanks