Dreamweaver can't connect to server

All my connections to sites developed using PHP/Mysql worked until recently.
I had a new client and was defining a site for the client. I had errors connecting to the database so I used the test connection button to test the site's configuration and it's saying dreamweaver cannot use the prefix to display live data. (HTTP Error: 2)

I've done everything I can think of but I still cannot get anything to work. I went to previous sites with completed projects (I had not deleted the files or site definition) and when I click on test, I get the same error. Strange as these were functioning ok and I was able to use them to create these sites.
Any help / suggestions would be deeply appreciated.