FYI Content 1.0.3 was just released which contains this, and other, fixes.

This is already fixed in git.

Note: this is actually Content 1.0.2 (but I could not select this for 
the ticket.

In function getSimilarObjects the HAVING clause uses the output name 
of a selected column. But according to the PostgreSQL doku, HAVING 
operates on the rows created by GROUP BY and thus can not use the 
output name.

As a result I get a fatal error with PostgreSQL:

2011-10-11T22:59:10+02:00 ERR: HORDE [ansel] SQL QUERY FAILED: 
SQLSTATE[42703]: Undefined column: 7 ERROR:  column "num_common_tags" 
does not exist
LINE 1: ...ct_id <> 2285 GROUP BY objects.object_name HAVING num_common...
                                                              ^
         SELECT objects.object_name, COUNT(matches.object_id) AS
           num_common_tags FROM "rampage_tagged" matches INNER JOIN
           "rampage_tags" tags ON (tags.tag_id = matches.tag_id) INNER JOIN
           "rampage_users" users ON users.user_id = matches.user_id AND
           users.user_name = 'thpo' INNER JOIN "rampage_objects" objects ON
           objects.object_id = matches.object_id INNER JOIN 
"rampage_types" types
           ON types.type_id=objects.type_id AND types.type_name = 'image' WHERE
           tags.tag_id IN (7) AND matches.object_id <> 2285 GROUP BY
           objects.object_name HAVING num_common_tags >= 1 ORDER BY
           num_common_tags DESC LIMIT 10 [pid 29125 on line 812 of 
"/usr/share/php/Horde/Db/Adapter/Base.php"]
2011-10-11T22:59:10+02:00 EMERG: HORDE [ansel] SQLSTATE[42703]: 
Undefined column: 7 ERROR:  column "num_common_tags" does not exist
LINE 1: ...ct_id <> 2285 GROUP BY objects.object_name HAVING num_common...
                                                              ^ [pid 
29125 on line 393 of "/srv/horde4/ansel/lib/Tagger.php"]