Gren,
I enabled those two debug options and have tried re-adding the calendar, but I am getting the same error...and not any other clues. It appears to read lots of calendar data from the server and then outputs the errors below...
Warning: There has been an error reading data for calendar: s. However, this error is believed to be minor, so the program will attempt to continue. Error code: 0x80004005. Description: failed to retrieve item
Warning: There has been an error reading data for calendar: s. However, this error is believed to be minor, so the program will attempt to continue. Error code: READ_FAILED. Description:
Curious, what version of Thunderbird are you on and what platform?
Also, from the 11.4.2 release notes:
Support for Lightning/Sunbird with initial support for Lightning 0.9
Wondering if this is a Scalix issue or a Lightning issue?