shecat on "database won't connect with my files"

Hi,
My WP blog was doing ok. sadly for me I started playing around with databases and file folders for it. I tried to put on a different site under same domain and ended up deleting all my blog. The hosting provider managed to recover everything, but here comes my problem:
I log into the database and see that everything's in place - all the entries are there.
I use filezilla and connect to files - everythings there-recovered.
But the site sends a message that it's unable to connect to database. I try changing the wp-config file and I think it looks good, but the db still won't connect.
What else aside the config might be wrong? What should I check or update that might help?
thanks a lot!
(the site: psaurok.pl)