This error doesn't happen in Win 7 and seems to only occur in Win 8 when debug flags are used. I have updated SharpDX libraries too and rebuilt but still have the issue.

A first chance exception of type 'SharpDX.SharpDXException' occurred in SharpDX.dll

An exception of type 'SharpDX.SharpDXException' occurred in SharpDX.dll but was not handled in user code

Additional information: HRESULT: [0x80040154], Module: [Unknown], ApiCode: [Unknown/Unknown], Message: Class not registered

This occurs when creating the XAudio device using the following code

xAudioDevice = new XAudio2(xAudioDebugFlags, ProcessorSpecifier.DefaultProcessor);

Using the default constructor doesn't give any errors however I want debug flags on so I use this. I have messed around a bit with flags / processor specifier and the error occurs when "XAudio2Flags.DebugEngine" is used. This is a normal desktop app and I have no other issues with running and for what it's worth no COM issues of my own, assuming this is a COM issue.