iManAdmin Class not registered Error

I'm trying to use the iManAdmin DLL (via reference to "C:\Program Files\Interwoven\WorkSite\Interop.iManAdmin.dll") for FileSite 8.5. I'm getting an exception saying a class is not registered. Here is the full error message

Retrieving the COM class factory for component with CLSID {72B028D1-6C83-11D4-AB0E-00C04F6803D1} failed due to the following error: 80040154 Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))

Here is the line of code where the exception occurs:

dms = New Com.Interwoven.WorkSite.iManAdmin.NRTDMS

Can someone please help me shed some light on this? I'm running this on a machine that just has FileSite installed. Does something else need to be installed, or do I need to register a DLL that isn't typically registered with FileSite?

-Rory