Changes have been made in Git (master):

commit 92d060ff722dd1f217ee2cecafb3129a6a136c30
Author: Michael M Slusarz <slusarz@horde.org>
Date:   Fri Nov 30 07:45:21 2012 -0700

     More poll list optimization

     Probably fixes Bug #11793

  imp/lib/Imap/Tree.php |   11 ++---------
  1 files changed, 2 insertions(+), 9 deletions(-)

http://git.horde.org/horde-git/-/commit/92d060ff722dd1f217ee2cecafb3129a6a136c30

I get lots of PHP ERROR: Array to string conversion [pid 9728 on line 
182 of 
"/home/jan/horde-develop/framework/Imap_Client/lib/Horde/Imap/Client/Utf7imap.php"] 
recently.

2012-11-30T12:20:36+01:00 DEBUG: Variable information:
array(4) {
   'a' =>
   class Horde_Imap_Client_Mailbox#255 (2) {
     protected $_utf7imap =>
     NULL
     protected $_utf8 =>
     string(2) "40"
   }
   'c' =>
   class Horde_Imap_Client_Mailbox#253 (2) {
     protected $_utf7imap =>
     NULL
     protected $_utf8 =>
     string(1) "0"
   }
   'p' =>
   class Horde_Imap_Client_Mailbox#252 (2) {
     protected $_utf7imap =>
     NULL
     protected $_utf8 =>
     string(5) "base\000"
   }
   'v' =>
   class Horde_Imap_Client_Mailbox#250 (2) {
     protected $_utf7imap =>
     NULL
     protected $_utf8 =>
     string(5) "INBOX"
   }
}

Backtrace:
  1. Horde_Core_Ajax_Application->send() 
/home/jan/horde-develop/horde/services/ajax.php:65
  2. Horde_Core_Ajax_Response->sendAndExit() 
/home/jan/horde-develop/framework/Core/lib/Horde/Core/Ajax/Application.php:192
  3. Horde_Core_Ajax_Response_HordeCore->send() 
/home/jan/horde-develop/framework/Core/lib/Horde/Core/Ajax/Response.php:55
  4. Horde_Core_Ajax_Response_HordeCore->_jsonData() 
/home/jan/horde-develop/framework/Core/lib/Horde/Core/Ajax/Response/HordeCore.php:42
  5. Horde_Notification_Handler->notify() 
/home/jan/horde-develop/framework/Core/lib/Horde/Core/Ajax/Response/HordeCore.php:65
  6. IMP_Notification_Handler_Decorator_NewmailNotify->notify() 
/home/jan/horde-develop/framework/Notification/lib/Horde/Notification/Handler.php:317
  7. IMP_Imap->statusMultiple() 
/home/jan/horde-develop/imp/lib/Notification/Handler/Decorator/NewmailNotify.php:56
  8. IMP_Imap->__call() 
/home/jan/horde-develop/imp/lib/Notification/Handler/Decorator/NewmailNotify.php:56
  9. call_user_func_array() /home/jan/horde-develop/imp/lib/Imap.php:388
10. Horde_Imap_Client_Base->statusMultiple()
11. Horde_Imap_Client_Base->status() 
/home/jan/horde-develop/framework/Imap_Client/lib/Horde/Imap/Client/Base.php:1727
12. Horde_Imap_Client_Socket->_status() 
/home/jan/horde-develop/framework/Imap_Client/lib/Horde/Imap/Client/Base.php:1635
13. Horde_Imap_Client_Data_Format_Mailbox->__construct() 
/home/jan/horde-develop/framework/Imap_Client/lib/Horde/Imap/Client/Socket.php:1400
14. Horde_Imap_Client_Mailbox->__get() 
/home/jan/horde-develop/framework/Imap_Client/lib/Horde/Imap/Client/Data/Format/Mailbox.php:39
15. Horde_Imap_Client_Utf7imap::Utf8ToUtf7Imap() 
/home/jan/horde-develop/framework/Imap_Client/lib/Horde/Imap/Client/Mailbox.php:88
16. Horde::debug() 
/home/jan/horde-develop/framework/Imap_Client/lib/Horde/Imap/Client/Utf7imap.php:182