An interesting problem at work that I forgot I knew the answer to. At the agency there is a set of very old Microsoft Access applications getting data from a very old MySQL 4.0 server. The server that the data base resides on is being replaced with a Dell 2950 and I want to upgrade all the software. With MySQL 5.1 installed the Access applications, using the 3.51 driver, could not connect to any of the databases. When checked against the DSN an error came back as: Client does not support authentication protocol.