[ingo] unknown error in activating script

[lst_hoe01@kwsoft.de]

Hello

We have a horde/imp/ingo installation which uses Cyrus and Sieve for 
managing redirects/vacation and the like. It has worked as intended but 
today one user reported that he can not revoke his vacation message. I 
have tried it with and other account and get the error message (german) 
"Beim Aktivieren des Skripts ist ein Fehler aufgetreten. Antwort des 
Treibers:"

I can not find anything in the logs and tcpdump does not even show a 
connect to timsieved.

Horde Applications

    * Horde: 3.0.10
    * Imp: H3 (4.0.4) (run Imp tests)
    * Ingo: H3 (1.1.1) (run Ingo tests)
    * Kronolith: H3 (2.0.6)
    * Passwd: H3 (3.0) (run Passwd tests)
    * Turba: H3 (2.0.4)

PEAR Modules reported by ingo

    * PEAR Search Path (PHP's include_path):  /srv/www/horde/lib:.:/usr/lib/php
    * PEAR: Yes
    * Recent PEAR: Yes
    * Net_Socket: Yes
    * Net_Sieve: Yes

Any hint where i can dig what is going wrong?

Thanxs for any help

Andreas