Why do I need to run my VS 2008 app in Compatibility Mode on Vista

Question

Hi,
I just finished working on a Windows application using .NET 3.5 Framework - developed in C# with Visual Studio 2008. I am now testing deployment and on the first Vista system I ran into (Home Premium SP1), I had to use Compatibility Mode to get my application to be allowed to run.
I would understand needing compatibility mode if this app was compiled some time ago with an older Visual Studio or .NET Framework, but this is new development with Visual Studio 2008 and .NET 3.5.  I can't believe that Visual Studio would not have support for Vista. Well I can believe it, but there should at least be some documentation.  
I feel like I missed an important memo about Vista deployments.
Am I missing a build or compile setting somewhere?
Also, what should I expect with Windows 7?
I appreciate any information that can be provided.