WEBI Authenticating through to SQL

In my organisation we have historically used SQL Server authentication for configuring ODBC connections to databases with generic accounts, but we are now finally moving to using Windows AD authentication.

As it stands, the only way I can make a full connection through to the database (thus populating a report) this way is by using WEBI Rich Client on a fully networked PC.

If I use the BI Launchpad client then it always tries to authenticate using a generic service account (which I can see is configured in the Server Intelligence Agent).

However, the thing that is confusing me is that when I connect using WEBI Rich Client while working from home (connecting via Microsoft Direct Access), it still somehow uses the same service account. I have ticked the box in Launchpad Preferences to enable the "J2EE Portal" option, which now allows me to autenticate through to universes to create queries, but any attempt to actually connect to the data results in a failed login for that same generic service account.

Does anybody know how I can configure Windows authentication all the way through to the SQL data when using WEBI RC from home like this?

Many thanks.