Can't get ads to show -> Solved

I installed this 'looks like a great' module, but I can't get the ads to show. Drupal 5.3. Tried both the 5.x-1.4 and 5.x-1.x-dev release. Also spend a few houres to read the issues but can't find the solution.

This is the debug output:

ad_dir: '/var/www/html/DRUPAL_SHARED_CODEBASE/modules/ad'
debug: '2'
cache: 'none'
nids: ''
tids: '0'
hostid: ''
quantity: '1'
aid: '0'
ad_display: 'javascript'
Drupal bootstrap '0'.
Root drupal directory detected as '/var/www/html/DRUPAL_SHARED_CODEBASE'.

/var/www/html/DRUPAL_SHARED_CODEBASE/modules/ad/serve.php: // $Id: serve.php,v 1.1.2.2 2007/10/19 02:46:40 jeremy Exp $
/var/www/html/DRUPAL_SHARED_CODEBASE/modules/ad/ad.module: // $Id: ad.module,v 1.2.2.29.2.62 2008/01/17 20:04:14 jeremy Exp $

No cache enabled.
Drupal bootstrap '7'.
Ads previously served: 0
Searching for ads with no tids.
Query: "SELECT a.aid, a.adtype, a.redirect, a.activated, a.maxviews, a.maxclicks FROM {ads} a LEFT JOIN {term_node} n ON a.aid = n.nid WHERE a.adstatus = 'active' AND n.tid IS NULL ORDER BY RAND() LIMIT 1;"
adserve_increment action(count) cache(none)
Drupal bootstrap '7'.
Ads displayed: 0
document.write('\x3c!-- No active ads were found in the tids \'0\'. --\x3e');

If I execute the query in mysql, I get one result (I have only one ad). I don't use ad-groups, I have one text ad, display block. Also doens't work when using image ad.

There might be one issue: we use a symlink to the modules folder which is at another path. In 'adserv.inc' should I specify the 'DRUPAL_ROOT' to the modules folder or the site root? Tried both...