What is the connection string being used?

Does this only happen on the VS 2010 system?

Can he connect to the Application database using the Server Explorer in VS 2010?

Does the VS 2010 system have MDAC 2.8 or better and SQL 10 Native SQL drivers installed?

My guess is what changed in your VB.NET app was the version of Visual Studio. If the app is over two years in production it could not have been created with VS 2010 originaly.

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