RtlVolumeDeviceToDosName might have something to do with it, or does it happen randomly? It may actually be coming from the IDE doing some housekeeping, as well.

Can you try putting your shader into a file, and using the CompileFromFile() method instead? Then we can compare what happens, to gain some insight into the problem. (if it works, then it's a problem with the byte array or with the Compile() method, and if it doesn't work we need to keep looking).

My guess is Malware Bytes Anti-Malware. Might be interferring; likely not.

CompileFromFile *Insert Wierd Al break, because my brain is leaking out my ears because I've been programming most of today, which is almost over* resulted in...

[4016]
[4016] *** HR originated: -2147024774
[4016] *** Source File: d:\iso_whid\x86fre\base\isolation\com\copyout.cpp, line 1391
[4016]
[4016]
[4016] *** HR propagated: -2147024774
[4016] *** Source File: d:\iso_whid\x86fre\base\isolation\com\identityauthority.cpp, line 278
[4016]

With null-check and

[4016]
[4016] *** HR originated: -2147024774
[4016] *** Source File: d:\iso_whid\x86fre\base\isolation\com\copyout.cpp, line 1391
[4016]
[4016]
[4016] *** HR propagated: -2147024774
[4016] *** Source File: d:\iso_whid\x86fre\base\isolation\com\identityauthority.cpp, line 278
[4016]

without null-check.

What loads the shader:

using (
// var byteCode = SlimDX.D3DCompiler.ShaderBytecode.Compile(
var byteCode = SlimDX.D3DCompiler.ShaderBytecode.CompileFromFile(
// Properties.Resources.Shader11,
"Shader11.fx",
"fx_5_0",
SlimDX.D3DCompiler.ShaderFlags.Debug,
SlimDX.D3DCompiler.EffectFlags.None
)
)
defaultEffect = new SlimDX.Direct3D11.Effect(dxDevice, byteCode);