E_FAIL error...DLL is looking to wrong directory

Hi all,

Been banging my head against the monitor on this for a while.  Hoping you can help.

I have a class calling a DLL, which references another class.  The code currently works in production, but I'm trying to move the code to a new server, and I get the dreaded E_FAIL error.  (Very helpful)

I can see in the stack trace, however, that the DLL seems to be looking for my class in the wrong directory:

[COMException (0x80004005): Error HRESULT E_FAIL has been returned from a call to a COM component.]
   ABCDE.OMI.XYZ.DoTheThing(String PSID) in C:\DevServer\WrongPath\TheThingHelper.cs:67
   utils.theThing(String username, String psid, String& msg) in e:\NewServer\CorrectPath\App_Code\utils.cs:218

In the example above, I can see the call to "DoTheThing(string PSID)" is looking to the same path as on my development box.  It SHOULD be looking to the path in the next line.  How do I fix that?!  Is there some kind of registration that needs to take place on the new server?