Emulator

What steps will reproduce the problem?

1. Start a copy of Dolphin SVN in fresh installed copy of windows (obviously with the last DirectX Redistributable installed and all the propper drivers)
2. Set the audio Backend to XAudio2
3. Start any game and wait.

What is the expected output? What do you see instead?
The expected output: The game should run without problems.
What do you see: The emulator shows a error that Audio Backend (XAudio) is invalid.

Dolphin version with the problem? Other Dolphin version without the
problem?
SVN R6623. But i don't know if this is a "version specific" problem.

32-bit or 64-bit and any other build parameters?

Dolphin X64. Dual core mode in JITL.

OS version and versions of tools/libraries used?

Windows 7 X64 Pro
Visual Studio 2008 Pro
Latest DirectX SDK (for build process)

Please provide any additional information below.
I think, should be something related to DX SDK libraries. Maybe there is a specific function that is not included in the "retail" DirectX or maybe some kind of dependency that is only satisfied by a developer environment.

Additionaly: Only when i install the SDK the problem dissapears completly.
If this is not a issue and is just a user missconfiguration... sorry.