Make sure that your connection parameters are correct and that your database server is up and running. Contact your support to verify that you have the correct data.
Connection problems are usually caused by database server problems or by bad connection parameters so we should start from there. As boxfan said, open config/config.php and make sure that data in it is valid. Your support should be able to check that for you and give you additional information.
Error params:
File: /home/dannyh/public_html/clients/environment/library/database/adapters/MysqlDBAdapter.class.php
Line: 32
#0 /home/dannyh/public_html/clients/environment/library/database/adapters/AbstractDBAdapter.class.php(40): MysqlDBAdapter->connect(Array)
#1 /home/dannyh/public_html/clients/environment/library/database/DB.class.php(93): AbstractDBAdapter->__construct(Array)
#2 /home/dannyh/public_html/clients/environment/library/database/DB.class.php(64): DB::connectAdapter('mysql', Array)
#3 /home/dannyh/public_html/clients/init.php(104): DB::connect('mysql', Array)
#4 /home/dannyh/public_html/clients/index.php(9): require('/home/dannyh/pu...')
#5 {main}
Can anyone tell me whats wrong?