I am working with FEZ Cobra.
After I reinstall the latest GHI SDK, I get error message when add a reference:
Incompatible reference
“GHIElectronics.NETMF.Native, Version 4.1.5.0, Culture=neutral, PublicKeyToken=null” is incompatible with .NET Micro Framework 4.1.2821.0
In order to add it you should to change the project’s target to a compatible framework first.
You need to update the firmware on the EMX to the same version.
Run MFDelpoy (it’s in C:\Program Files\Microsoft .NET Micro Framework\v4.1\Tools )
Choose USB and click device capabilities, scroll up in the output window and look at the solution version. It needs to be 4.1.5.0.
Also if you are using an exsisting example, you need to delete all GHI references in the solution panel on the right and renew them (a copy is placed in the projects folder and needs updating )
Cheers Ian
Your error message gave you the hint already:
You have a version difference between 4.1.5.0 and 4.1.2821.0.
Update your firmware as Ian suggested.
I updated firmware. Error is in Visual Studio 2010.
Are you sure you followed the exact instructions on installing the correct Microsoft NETMF SDK and GHI NETMF SDK?
Can you make a new “NETMF console project”? This is the first thing you do if you follow the book. This doesn’t need any GHI assemblies.
Why do you need the (GHIElectronics.NETMF.Native) references anyway are you using RLP?
Are you deploying to an EMX or to the emulator? As the GHI references are not recognised by the emulator.
Cheers Ian
@ Gus… The publicKey is null does the deploy this need this key
First I uninstalled previous GHI SDK and check that SDK folders are deleted.
After that I installed the latest GHI SDK and update firmware on FEZ Cobra.
I made simple NETMF console project without GHI assemblies and deploy successfully to FEZ Cobra. When I try to add reference (GHI dll’s) I got that error.
I use Visual Studio 2010 ultimate with SP1.
Any GHI dll or just this one (.native)
Cheers Ian
Any GHI dll. 
Just double checking.
You get the firmware file from:
…\GHI Electronics\GHI NETMF v4.1 SDK\EMX\Firmware
Is that correct?
Yes, that is correct.
I found same error report on FEZ Domino, Mini and Panda forum (problems with GHIElectronics.NETMF.Hardware reference FEZDOMINO).
It works fine here… VS2010 express and 4.1.5.0 assemblies panda , panda2 and cobra deploy ok…
Just double checking… You have deleted all references in the solution panel and renewed…
Cheers Ian
Are you using some power tools? maybe that’s why.
Thank you Mike!!! 
I deinstalled from Extension Manager all power tools and everyhting is OK now.
Thank you once again for your support.
We should have known this!!! We had this same problem some months back.
Architect’s right about the search…
Cheers Ian