It is still pointing to the correct database?
Open your config file. It should be one of the following:
/include/ost-config.pgp
/include/ostconfig.php
/include/settings.php
Scroll down to #Mysql Login Info. Specifically look at DBNAME, DBUSER, and DBPASS. Also while you are here you might want to make sure that TABLE_PREFIX is correct also.
Out of curiosity did you ever remove the /setup dir?