Cobra Internal Error with IronPython (mscorlib)

[Kurper]

With IronPython? 2.7, and the @ref'd DLLs copied from IronPython/Silverlight?/bin into my bin directory, I get the following error:

me@LAPBOT ~/code/sherlock/bin (master)
$ cat test.cobra
@ref "IronPython?.dll"
@ref "Microsoft.Dynamic.dll"
@ref "Microsoft.Scripting.dll"
@ref "IronPython?.Modules.dll"
use IronPython?

class Poo

def main

pass

me@LAPBOT ~/code/sherlock/bin (master)
$ cobra test.cobra
error: COBRA INTERNAL ERROR / TypeLoadException? / Could not load type 'System.Co
llections.IStructuralEquatable' from assembly 'mscorlib, Version=2.0.0.0, Cultur
e=neutral, PublicKeyToken?=b77a5c561934e089'.
Compilation failed - 1 error, 0 warnings
Not running due to errors above.

If I downgrade to IronPython? 2.6.1, instead I get:

error: COBRA INTERNAL ERROR / BadImageFormatException? / Could not load file or a
ssembly ' file:///c:\Users\me\code\sherlock\bin\IronPython.dll' or one of its dep
endencies. This assembly is built by a runtime newer than the currently loaded r
untime and cannot be loaded.

I'm using Cobra from SVN.