Sunbird/Lightning CalDAV not working.

I've managed to get it working in iCal (osx), on an iPad/iTouch, in 'windows calendar' using the [...]/zulu/calendars/<filename>/ entry.
I've also managed to download the file with [...]/zulu/calendars/<filename>/<calendar_uuid>/ successfully.
But Sunbird (1.0b1) and lightning (1.0b2), while opening the downloaded file, are not working with this entry in as a remote CalDAV item. (as specified in the 'Your Calendar Has Been Published!' page after the publishing.
Is there an error in my setup perhaps? Or is sunbird/lightning already known to be unhappy with Zulu at current?
I've also managed to download the file with [...]/zulu/calendars/<filename>/<calendar_uuid>/ successfully.
But Sunbird (1.0b1) and lightning (1.0b2), while opening the downloaded file, are not working with this entry in as a remote CalDAV item. (as specified in the 'Your Calendar Has Been Published!' page after the publishing.
Is there an error in my setup perhaps? Or is sunbird/lightning already known to be unhappy with Zulu at current?