One quick thought is that DataSource connections are handled at the web container level. You will need to make sure that the ODBC driver is available there. E.g., in
Tomcat 5.5. it has to be in the common/lib directory.
Also, you may be having class loader security problems if you have the JDBC jar in the web apps lib directory and at the container level. E.g., the class is initially loaded at the server level and now your webapp is trying to make the server use a class from it's library. This is a security issue and most containers will deny it (generally in strange ways like class not found errors...)
Try removing the jdbc jar from the web app.
[originally posted on jforum.net by monroe]