Claiming the user for a poor error message seems not to be the best 
user-friendly approach...

The UPGRADING document quite explicitly states that

     "The ActiveSync configuration section should be revisited."

If you decide to just go ahead and ignore this, the problem is all 
yours. As an administrator you should know better.

In this case, the error message generated when trying to update the 
horde config file should be way better than the current one. It's just 
stating that it cannot update the config file... The best would be to 
state that new parameters are not set and open the config to the tab 
where are the missing parameters.

Straight from the annoucement message:

For upgrading instructions, please see
http://www.horde.org/apps/horde/docs/UPGRADING

You'll find that quite a few changes are listed for ActiveSync. Go to 
the ActiveSync tab in the horde configuration and fill in the missing 
parameters.

Hi,

Just upgraded my Horde 5.1.7 to Horde 5.2 final and during the upgrade 
through pear, I got this syslog message:
Message from syslogd@box1 at Jul  9 12:11:57 ...
  HORDE: [horde] Missing required state object [pid 29235 on line 122 
of "/usr/share/php/Horde/ActiveSync/Driver/Base.php"]
I updated the DB and config files expecting to fix the issue.

But I still got the syslog message happening again and again.

So I tried to clear all the active sync devices to start fresh but 
once I click on ActiveSync Devices I got this fatal error:
A fatal error has occurred

Call to a member function setLogger() on a non-object

1. Horde_ErrorHandler::catchFatalError()
Details

The full error message is logged in Horde's log file, and is shown 
below only to administrators. Non-administrative users will not see 
error details.

ErrorException Object
(
     [message:protected] => Call to a member function setLogger() on a 
non-object
     [string:Exception:private] =>
     [code:protected] => 0
     [file:protected] => /.../horde/admin/activesync.php
     [line:protected] => 25
     [trace:Exception:private] => Array
         (
             [0] => Array
                 (
                     [function] => catchFatalError
                     [class] => Horde_ErrorHandler
                     [type] => ::
                     [args] => Array
                         (
                         )

                 )

         )

     [previous:Exception:private] =>
     [severity:protected] => 1
     [logged] => 1
)