THE PROBLEM WAS SOLVED WHEN I UPLOADED THE LAST GANTRY VERSION... which I thought I was getting when I uploaded Crystalline... 
Hi,
I installed the "Bundled" Crystalline (WITH the Gantry framework) a couple of weeks ago and then used mainly Refraction.
Yesterday I installed the "standalone" Panacea template and it seemed to work fine until I tried to edit the template in Template Manager. Here are the error messages I get:
Le fichier Paramètres /templates/rt_panacea_j15/params.ini est Modifiable!
Warning: require_once(/home/wwncaoff/public_html/libraries/joomla/html/parameter/element/html.php) [function.require-once]: failed to open stream: No such file or directory in /home/wwncaoff/public_html/components/com_gantry/admin/elements/chain.php on line 41
Fatal error: require_once() [function.require]: Failed opening required '/home/wwncaoff/public_html/libraries/joomla/html/parameter/element/html.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/wwncaoff/public_html/components/com_gantry/admin/elements/chain.php on line 41
That file is definitely not there in the .zip files we receive with the Joomla 1.5.18 install. So what's the problem and how can I solve it?
I hope I can solve this quickly.
Thanks!
Marie-Andree