Fixed in Git.

I have the same problem and debugged a bit:

On my system, every time I try to sync anything (regardless if 
calendar, mail or contacts) with my Android phone and one specific 
account it got stuck with the exception "_logger is not a valid 
property" which probably also caused segfaults.

The code where it happens is in Horde/ActiveSync.php, around line 650.
I can't get the original line numbers since I added some extra debug code.

It is around here, near the bottom of the function handleRequest():

public function handleRequest($cmd, $devId) {
  ......
         $class = 'Horde_ActiveSync_Request_' . basename($cmd);
         $version = $this->getProtocolVersion();
         if (class_exists($class)) {
             $request = new $class($this, $device);
             $request->setLogger($this->_logger);
---->    $result = $request->handle();     <---- here it crashes
             $this->_driver->clearAuthentication();
             return $result;
         }


I tracked it down to the 
Horde_ActiveSync_SyncCache::updateCollection() function. Whenever I 
try to access $this->_logger there the whole thing crashes, even when 
I just try to make a var_dump() on it.

So I commented out the Logging, cleared the caches, removed the device 
from Horde and tried again. Now it stops whith this error:

PHP Fatal error:  Cannot use object of type 
Horde_ActiveSync_Folder_Collection as array in 
/usr/share/pear/Horde/ActiveSync/State/Base.php on line 380


This might be a local problem with my PHP installation which is PHP 
5.3.3 on a CentOS 5.x system, but it sound very similar to the problem 
of the ticket opener!

Resolving since the original issue is fixed.

I would need a copy of such a message in order to help you track this down.

Sorry for the late response.
The error indeed disappeared after removing the device.

I updated to the latest git again yesterday and i now have a new 
error, but only when using Android devices, for iPhones it seems to 
work.

When i try to sync my Android phone or tablet, the php-fpm process 
segfaults when it reaches an Outlook HTML mail. The last message i see 
in the log is:
"Sending HTML message."

The Android device reports:
"Couldn't connect to server ..."

As soon as i delete+expunge the message in question, everything is 
working like a charm.

With an iPhone and the same message in the mailbox there is no problem at all.
Calendar and Contacts sync and GAL access is working on Android 
devices without problems.

I have no clue how to track this further down.

I can't reproduce this, and I can't really see how this would happen 
unless your state table became corrupt. During a FOLDERSYNC request, 
$this->_folder is, indeed, an array that contains all of the folder 
information that the device knows about. This is used to generate a 
diff against the current set of folder information on the server.

Can you try to remove the device from Horde and try again? If this 
still happens, I will need a complete synclog that covers the time 
from device pairing until the symptom presents again.

After the latest ActiveSync changes in git i get the follwoing php error:

"PHP message: PHP Fatal error:  Cannot use object of type 
Horde_ActiveSync_Folder_Collection as array in 
/home/www/horde/libs/Horde/ActiveSync/State/Base.php on line 346"
request: "POST 
/Microsoft-Server-ActiveSync?Cmd=FolderSync&User=********&DeviceId=androidcXXXXXXXXXX&DeviceType=Android 
HTTP/1.1"

Any fix is much apreciated.