Ok it can't access the calendar database any more without specifying the exact reason.

Can you try the following (again in the Terminal) and post the output (you can use copy & paste or use the "| tee ..." bit to save it to the debug.txt file again):

accli -p $(pgrep organiser) -I

(the last bit is an upper case i)

and

ls -al /home/user/.calendar/db

Thanks