What is ManagedMD.ILMethodException?

When I run permcalc on my Managed C++ DLL I get the following:
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..
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Microsoft (R) .NET Framework Permissions Calculator.
Copyright (C) Microsoft Corporation 2005. All rights reserved.

Analyzing...
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................................................................................
Generating output...
An error has occurred: The constructor to deserialize an object of type
'ManagedMD.ILMethodException' was not found.
..
..
..


I searched my hard drive and can't find any references to "ManagedMD". A
Google search turns up nothing, as does an MSDN search. What is this?
How do I fix it? I'm using .NET 2.0



Thanks,
--Jeremy
.