Registering VB.NET COM plugin for Windows Media Service

I'm trying to register a VB.NET plugin for Windows Media Service (on Windows 2003 Enterprise Server), and I'm having some odd problems...
As the Microsoft Platform SDK docs instruct, I copy the dll to:

Code:

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C:\WINDOWS\system32\windows media\server

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But then when I run RegAsm, I get this error:

Code:

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C:\WINDOWS\system32\windows media\server>regasm MyCustomPlaylist.dll
Microsoft (R) .NET Framework Assembly Registration Utility 2.0.50727.42
Copyright (C) Microsoft Corporation 1998-2004.  All rights reserved.

RegAsm : error RA0000 : Unable to locate input assembly 'MyCustomPlaylist.dll' or one of its dependencies.

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The odd thing is, if I run RegAsm on it when it's not in that directory, I get a wholly different error:

Code:

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C:\WINDOWS\system32\windows media\server>regasm m:\shared\devel\MyCustomPlaylist.dll
Microsoft (R) .NET Framework Assembly Registration Utility 2.0.50727.42
Copyright (C) Microsoft Corporation 1998-2004.  All rights reserved.

RegAsm : error RA0000 : Could not load file or assembly 'interop_msxml, Version=2.0.0.0,
Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The
located assembly's manifest definition does not match the assembly reference.
(Exception from HRESULT: 0x80131040)

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Now, I ran into a similar error about interop_msxml when trying to build the plugin (on a WinXP machine). That had to do with interop_msxml.dll not being correctly strong-named, and was fixed by this kb article. This new problem though is on a Win2K3 server, and I don't even know where to start...