I have a weird mistake, I'm working on Magento (1.5.1) but since I don't know when, installation scripts of modules doesn't work anymore, Magento seems not running SQL folders, for every kind of module. I tried to make a basic external php script using PDO and the same connection setting (host, dbname, loggin, pwd) and that works so I guess it's not a SQL permission problem. I'm totally disappointed.
(sorry for that bad English... of course I'm French)
Have a nice day !