I am getting an error "DB Error: unknown error" ONLY in the frontend of my website, but the admin area works fine. It happens when I switch my MYSQL server type from localhost:3306 to localhost:/var/lib/mysql/mysql.sock. The socket connection works fine on other joomla installs on the same server.

This Joomla install formerly had jms installed on it, but I had to uninstall it because of extension compatibility. I am not 100% sure jms caused it, but thought I might ask anyway. I've reuploaded all core Joomla files to be sure there isn't any issue, now it seems like a database problem. Thanks for your help.

Sorry but I don't see where the problem could come from.

Are you using another DB type - other than MySQL or MySQLi ?