These aren't errors, they are strict warnings.  Disable them in 
php.ini if you don't want to see them.

Additional error messages when clicking on a contact in debug mode. I 
don't see any problems with the VFS.

DEBUG: HORDE [turba] PHP ERROR: Non-static method 
Horde_Form_Action::factory() should not be called statically, assuming 
$this from incompatible context [pid 41331 on line 73 of 
"/horde/turba/lib/Form/ContactBase.php"]

DEBUG: HORDE [turba] PHP ERROR: Declaration of 
Horde_Form_Action_updatefield::getActionScript() should be compatible 
with Horde_Form_Action::getActionScript($form, $renderer, $varname) 
[pid 41331 on line 128 of "/php/Horde/Autoloader.php"]

DEBUG: HORDE [turba] PHP ERROR: Declaration of 
Horde_Form_Action_updatefield::setValues() should be compatible with 
Horde_Form_Action::setValues(&$vars, $sourceVal, $index = NULL, 
$arrayVal = false) [pid 41331 on line 128 of 
"/php/Horde/Autoloader.php"]

DEBUG: HORDE [turba] PHP ERROR: Declaration of 
Turba_Form_EditContact::renderActive() should be compatible with 
Horde_Form::renderActive($renderer = NULL, $vars = NULL, $action = '', 
$method = 'get', $enctype = NULL, $focus = true) [pid 41331 on line 
128 of "/php/Horde/Autoloader.php"]

Turba is the only app with a conf.d folder
File permissions on both the folder and file are the same as the other files

Content of file:
<?xml version="1.0"?>
<!-- $Id$ -->
<configuration>
  <configsection name="documents">
   <configvfs switchname="type">horde</configvfs>
  </configsection>
</configuration>


The patch helped as now contacts can be edited

Sorry... this is not limited to conf.d.  It could be any *.d directory 
- there's no way of tracing with the error message/details provided.

Can't reproduce.

Changes have been made in Git (master):

commit f254da8f6f7547818eaf3f9ac20f46098ca5a090
Author: Michael M Slusarz <slusarz@horde.org>
Date:   Tue Jul 8 23:50:38 2014 -0600

     [mms] Better error handling when trying to load config files from 
the conf.d subdirectory.

     Bug #13333

  framework/Core/lib/Horde/Registry/Loadconfig.php |    4 ++--
  framework/Core/package.xml                       |    4 ++--
  2 files changed, 4 insertions(+), 4 deletions(-)

http://github.com/horde/horde/commit/f254da8f6f7547818eaf3f9ac20f46098ca5a090

You've created a horde/config/conf.d directory and it's most likely 
inaccessible to the PHP user (glob() is returning false).

Here is what I see in the logs
T01:33:20+02:00 WARN: HORDE [turba] PHP ERROR: array_merge(): Argument 
#2 is not an array [pid 88976 on line 66 of 
"/php/lib/php/Horde/Registry/Loadconfig.php"]

The configuration has been generated from the interface and only 
contains this:
$conf['menu']['import_export'] = true;
$conf['shares']['source'] = 'localsql';
$conf['comments']['allow'] = true;
$conf['documents']['type'] = 'horde';
$conf['tags']['enabled'] = true;

After an upgrade from 4.1 to 4.2, I can pick any contact from the 
default address book and Turba will crash

A fatal error has occurred
You must configure a VFS backend.
1. Turba_View_Contact->html() /horde/turba/contact.php:126
2. Turba_Form_Contact->__construct() /horde/turba/lib/View/Contact.php:42
3. Turba_Object->vfsInit() /horde/turba/lib/Form/Contact.php:58
4. Turba_View_Contact->html() /horde/turba/contact.php:126
5. Turba_Form_Contact->__construct() /horde/turba/lib/View/Contact.php:42
6. Turba_Object->vfsInit() /horde/turba/lib/Form/Contact.php:58
7. Horde_Core_Factory_Vfs->create() /horde/turba/lib/Object.php:564
8. Horde_Core_Factory_Vfs->getConfig() 
/usr/local/php/lib/php/Horde/Core/Factory/Vfs.php:48

A file based VFS is configured in Horde and the turba config is using 
the Horde default.