I got it: 

the first time i set up the mediawiki with a db-username already existing (for other dbs). As a result, the MEdiaWiki was working allright with the DB, but the SemWiki extension was getting confused I guess. 

Then I re-installed the Media Wiki, and created a new db-username. The media wiki surprisingly added three users (instead of one): one with "%" as host-name, one with "localhost", and one with "localhost.localdomain". Just had to add some privileges to the "localhost" one and everything worked out fine.
If all this sounds pretty naive, im sorry i never played with wiki-installations before! 

Begin forwarded message:

From: Michele Pasin <m.pasin@open.ac.uk>
Date: 26 October 2006 18:33:07 BDT
To: semediawiki-user@lists.sourceforge.net
Cc: Denny Vrandecic <denny@nodix.de>
Subject: error with SQL-tables-creation

Hi all, 
is there anyone who can help me? I keep getting this error while installing:
A database query syntax error has occurred. This may indicate a bug in the software. The last attempted database query was:

    (SQL query hidden)

from within function "SMW::MakeSemanticTables". MySQL returned error "1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '-wiki.`smw_relations` ( subject_id INT(8) UNSIGNED NOT NULL, s' at line 1 (localhost)".
I'm trying to install SemWiki on a mac runninng osX.4,  PhP 5, MySql 5.....
In LocalSettings.php, DB name, user and psw are written down, and are correct. The user has all privileges...



Michele Pasin

Phd Student

Knowledge Media Institute

The Open University

Walton Hall

Milton Keynes


United Kingdom

Tel: 01908 858730

Email: m.pasin@open.ac.uk

< www.kmi.open.ac.uk/people/mikele >