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?

We know that Lightening doesn't work- or at least we haven't got it working yet. But Sunbird should without the lightening extension. Am I reading you right that Sunbird is also failing to pick this up?

Yes, I've tried setting up on both standalone Sunbird (1.0b1 - windows) and lightning (1.0b2 in thunderbird - also windows.) They react identically, they think for a bit, they appear to download some kind of information (I see a network traffic bump, although I haven't done actual network traffic sniffing.)

Then just nothing shows up. I have noticed that sometimes after attempting to load the remote calendar, it sometimes stops showing even the locally loaded file until I restart. I tried it without any other calendars loaded as well, still couldn't get a remote calendar to show up.

I'm running on a windows vista x64 platform, I think I'll check it with Sunbird on some of my other machines (XP and OSX) to make sure I'm not encountering something in the environment, as I know the sunbird/lightning product has always been rather spotty.

(But seeing the database showing up on the iPad calendar, then creating a new entry from the iPad is unbelievably incredible!)

Warning: There has been an error reading data for calendar: Tours. However, this error is believed to be minor, so the program will attempt to continue. Error code: DAV_NOT_DAV. Description: The resource at http://<www>:8040/zulu/calendars/SOLUTION/6d71e922-83a0-44f5-98c7-d0b500206a9b/ is either not a DAV collection or not available

Warning: There has been an error reading data for calendar: Tours. However, this error is believed to be minor, so the program will attempt to continue. Error code: READ_FAILED. Description:

(<www> and SOLUTION are placeholders)

In the calendars list, it has a warning triangle with a '!' and says 'The calendar Tours is momentarily not available' on the tooltip.

This is occuring on:
Vista x64 SP2 w/sunbird 1.0b1
OSX 10.6.4 (32bit) w/sunbird 1.0b1
WHS SP2 (32bit, aka server 2003/XP) w/sunbird 1.0b1

I updated to 0.993 zulu (I think it was 0.992? the other day when I first got it) and no change.

iCal on the mac reloaded fine, Windows calendar reloaded fine, iPad, iTouch reloaded fine.