This post is relevant if you have a Magento database error, likely because you have:
1. Moved your Magento installation to a new host
2. Changed the username and/or password to the database
You will see a problem in /var/reports/xxxxx saying something about “Access denied for user” and “Zend_Db_Adapter_Pdo_Abstract->_connect()”
Here is what to do:
1. Change app/etc/config.xml to reflect your host, databasename, username and password
2. Change app/etc/local.xml, with the information from step 1.
3. Clear your cache, remove all files in /var/cache
And you are ready to go. Omitting step 2 and 3, which you are likely to do if it is the first time you try this, will normally not fix the problem.