Error conexion database upgrade 1.7.2

[eluser]tnathos[/eluser]
Hi.. i make a copy from my proyect in version 1.7.1, later download the version 1.7.2 and replace the folders what in the user guide indicate.

system, config, database, helper, languaje, libraries.

But when run the proyect doesnt works!! i chek the mesaages and i find what the app dont conect to the database.. again.. restore my backup whit 1.7.1 and run.. again upgrade the site and not conect to the database..

I development in a mac SO leopard using MAMP. any how i can reslve this? because i need the helper cart!!! xd