Trying to connect to a MySQL DB i get that error. This used to work fine a couple of months ago when I first made the panel. I can access from Mysql Query tool but not from Tableau.
I already repaired the MySQL ODBC drivers in my Windows 7x64 machine. This also happens to a coworker who i gave the workbook to check.
My guess is that the mySql user Tableau is using to connect is configured with the old password hashing .
Tableau tries to connect using the new hashing, which is probably not the case with your Query tool.
You should ask the DBA to make sure the user password is encrypted with the new hashing.