Thunderbird and Lightning Fixes
Remote ICS calendar not working, shows momentarily not available
There are UTF8 characters in the feed. Download the ICS file
Find the UTF8 characters
iconv -c -f utf-8 -t ascii tripit.ics | diff --unified=5 tripit.ics -
Login to the calendar provider and fix the event.
If this did not help open the error console in thunderbird and refresh the calendar in question by checking or unchecking the "offline support" option in the calendar properties.
CalDAV or davmail fronted calendar is not working after a password was changed
Sometimes Lightning does not process 'authentication failed' errors correctly and does not prompt for the new password.
To resolve this open Thunderbird, go to Edit -> Preferences -> Security -> Passwords -> Saved Passwords... and delete the offending record(s).
Restart DavMail as well, it seems to keep something related to the authentication mechanism cached.