I disagree with you on that.

Bug #9725 just states, that you cannot use the ILIKE operator on 
arguments, that do not have this operator implemented.
If it were the same bug, it would disappear, when you disable the LIKE 
-> ILIKE conversion. (which I did for a test, and it did not disappear)

In my opinion this bug might be about binary data that is not base64 
encoded before using it in a query.

No, it looks like it's *exactly* the same like bug #9725.

Sorry, my attached vcf got lost in submission.

When trying to import a vCard (either via syncml or using 
/turba/data.php) I get the following error:

2011-07-26T08:03:28+02:00 ERR: HORDE [turba] SQL QUERY FAILED: 
SQLSTATE[22021]: Character not in repertoire: 7 ERROR:  invalid byte 
sequence for encoding "UTF8": 0xb7
TIP:  This error can also happen if the byte sequence does not match 
the encoding expected by the server, which is controlled by 
"client_encoding".
         SELECT object_id, owner_id, object_type, object_members, object_uid,
           object_firstname, object_lastname, object_middlenames,
           object_nameprefix, object_namesuffix, object_alias, object_bday,
           object_photo, object_phototype, object_homestreet, object_homepob,
           object_homecity, object_homeprovince, object_homepostalcode,
           object_homecountry, object_workstreet, object_workpob,
           object_workcity, object_workprovince, object_workpostalcode,
           object_workcountry, object_tz, object_email, object_homephone,
           object_workphone, object_cellphone, object_fax, object_pager,
           object_title, object_role, object_company, object_logo,
           object_logotype, object_category, object_notes, object_url,
           object_freebusyurl, object_pgppublickey, object_smimepublickey FROM
           turba_objects WHERE (owner_id = 'thpo' AND 
(((object_nameprefix ILIKE
           '%Test%' OR object_nameprefix ILIKE '%User%' OR (object_nameprefix =
           '' OR object_nameprefix IS NULL)) AND (object_firstname 
ILIKE '%Test%'
           OR object_firstname ILIKE '%User%' OR (object_firstname = '' OR
           object_firstname IS NULL)) AND (object_middlenames ILIKE '%Test%' OR
           object_middlenames ILIKE '%User%' OR (object_middlenames = '' OR
           object_middlenames IS NULL)) AND (object_lastname ILIKE '%Test%' OR
           object_lastname ILIKE '%User%' OR (object_lastname = '' OR
           object_lastname IS NULL)) AND (object_namesuffix ILIKE '%Test%' OR
           object_namesuffix ILIKE '%User%' OR (object_namesuffix = '' OR
           object_namesuffix IS NULL))) AND object_lastname ILIKE '%User%' AND
           object_firstname ILIKE '%Test%' AND object_photo ILIKE 
'%i<B7>^]%' AND
           object_phototype ILIKE '%png%')) [pid 7729 on line 808 of 
"/usr/share/php/Horde/Db/Adapter/Base.php"]


I have tried to play around with some character encoding settings in 
Horde and PostgreSQL, but it did not solve the problem.

My current settings are:
  - in horde/config/conf.php:$conf['sql']['charset'] = 'utf-8';
  - in the database both client_encoding and server_encoding are set to UTF8

As a workaround for this bug, I have currently added the following 
line to my turba/config/backends.local.php:
  unset($cfgSources['localsql']['map']['photo']);

Please note, that this bug is closely related to Bug #9725. But in my 
opinion these are two seperate issues in the same code region.