[horde] No calendar for new users

[Harlan]

Hello,
   I've created a few users on my Horde system.  The original ones I 
created are working fine and I can use their calendars.
   Lately, after upgrading to 5.2.22, I can still create the users just 
fine, but they don't have calendars.

   When I login with their usernames, in the Portal for the Calendar 
section I see this error:
     SQLSTATE[42S22]: Column not found: 1054 Unknown column 
'attribute_default' in 'field list'

   When I Google the error, the only suggestion I see to change the 
driver.  This is what I have for the drivers:

$conf['calendar']['driver'] = 'sql';
$conf['storage']['driver'] = 'sql';
$conf['calendars']['driver'] = 'kolab';

   One thing I didn't notice before is the 'kolab' above.  I don't have 
a Kolab server running.

   What is the difference between 'calendar' and 'calendars' above?
   Should the 'calendars' also be set to sql since I am using the database?

   I'm running on Debian.  Horde Groupware Webmail Edition 5.2.22, 
Kronolith 4.2.23.  I installed Horde via pear, and upgraded via pear also.

   Any idea why my later users don't have calendars?
   And what do I need to fix to get their calendars working?

Thanks,

Harlan...