[horde] Error with monthly IMP tasks

[Jens Grüntjes]

Hello list,

when I logged in to horde this morning I was asked if I wanted to do  
the monthly "clean-up-tasks". I clicked OK and then this error message  
appeared in the browser (sorry, but it's partially in Germn):


Ein schwerer Fehler ist aufgetreten:
Class 'IMP_Imap_Ftree_IteratorFilter' not found

1. Horde_ErrorHandler::catchFatalError()

Details
Die vollständige Fehlermeldung wurde in Hordes Logdatei geschrieben  
und für Administratoren weiter unten ausgegeben. Benutzer, die keine  
Administratoren sind, bekommen diese Details nicht zu sehen.

ErrorException Object
(
     [message:protected] => Class 'IMP_Imap_Ftree_IteratorFilter' not found
     [string:Exception:private] =>
     [code:protected] => 0
     [file:protected] =>  
/var/www/horde/imp/lib/LoginTasks/Task/DeleteSentmailMonthly.php
     [line:protected] => 45
     [trace:Exception:private] => Array
         (
             [0] => Array
                 (
                     [function] => catchFatalError
                     [class] => Horde_ErrorHandler
                     [type] => ::
                     [args] => Array
                         (
                         )

                 )

         )

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

This is the message in the log file:
2014-08-01T06:18:17+00:00 EMERG: HORDE [imp] Class  
'IMP_Imap_Ftree_IteratorFilter' not found [pid 30960 on line 45 of  
"/var/www/horde/imp/lib/LoginTasks/Task/DeleteSentmailMonthly.php"]

Is it an error in my setup or is it an error in horde? I'm using the  
latest PEAR package (last upgrade on Tuesday).

Greetings
Jens