After upgrade to 1.1.0: Problems with identity_smtp and carddav

[plumbington]

Very happy now!!

Was too quick with the happy!

We're still experiencing issues with the CardDav plugin.  Sometimes it works, and sometimes it doesn't??!!

I found some possibly related log entries:

in logs/carddav.warn, I'm seeing lines like this:
    [09-Apr-2015 09:06:57 -0400]: <5fc3kn11> BACKEND: (cdfopen) Could not read reply header: authentication error: 404 Not Found
    [09-Apr-2015 09:07:27 -0400]: <5fc3kn11> BACKEND: (refreshdb_from_server) Errors occurred during the refresh of addressbook 1

and in logs/errors
    [09-Apr-2015 14:17:07 -0400]: <smi68llv> PHP Error: Addressbook source () not found! in /usr/local/topicdesk/roundcube/WebApp/program/include/rcmail.php on line 252 (GET /webmail/?_task=addressbook)

Is there any way to turn on additional diagnostics/debugging for the CardDav plugin?

We're running RoundCube v1.1 and the CardDav plugin v0.8.1-dev on a Mac OS X 10.10.3 Server

Any pointers on how to proceed would be appreciated.