Das Werkstatt

[PROBLEM]
Just ran into the following error when I tried to add an additional CalDAV calendar (source OwnCloud), but:

Error: [calCachedCalendar] replay action failed: null, uri=https://www.my-server.example/owncloud/ ... ser/myuser, result=2147500037, op=[xpconnect wrapped calIOperation]
Source: file:///C:/Users/me/AppData/Roaming/Thunderbird/Profiles/xxxxxx.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/calendar-js/calCachedCalendar.js
Line: 322

Adding that calendar as the first (or only) calendar works fine, but not if other CalDAV calendars already exist in Lightning...

[SOLUTION]
The error message is very cryptic, but the issue is actually that Lightning seems to handle credentials per-hostname.
Therefore, a workaround we've currently applied is to use a different hostname (for the same OwnCloud server) for a calendar that requires different credentials.

Not super-beautiful, but for my case it did the trick!
(Thanks Gil for figuring that out)

You might get this error also if you previously had CalDAV calendars registered in Lightning, and the credentials stored by Thunderbird's password manager.
In that case, do the following:

1) Remove the stored password for the affected CalDAV host.
You might want to follow the instructions shown in this HowTo: "Thunderbird - Changing the Stored Password"

2) Restart Firefox

After restarting firefox, you should now be asked again for the login credentials for the CalDAV host.